Hubbry Logo
Barrel threadsBarrel threadsMain
Open search
Barrel threads
Community hub
Barrel threads
logo
7 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Barrel threads
Barrel threads
Barrel threads
View on Wikipedia
from Wikipedia

In firearms, barrel threads refer to the screw threads used to attach a barrel.[1]

Action threads, also called receiver threads, are situated at the chamber end of the barrel, and can be used for attaching the barrel to the receiver. The receiver normally has corresponding threads which are internal, with the matching action threads on the barrel usually being external threads. This design is most commonly used in rifles and revolvers, but also on some pistols and shotguns. This method of fixing a barrel to a receiver has been used extensively by firearms manufacturers since before the 20th century,[citation needed] and can be viewed as a traditional barrel mounting method. Action threads are not the only method of fixing a barrel to a receiver (see Alternative methods below). Furthermore, recoil-operated firearm designs have moving barrels (e.g. most pistols or the Barrett M82 rifle).

Muzzle threads are situated at the muzzle end of the barrel and can be used for mounting accessories such as a flash hider, suppressor or muzzle brake (compensator).

Designation

[edit]

There are many systems for designating thread types (metric, unified, Whitworth, etc.). Threading can be specified by diameter, pitch, angle, length and fit tolerances. However, the use of action threads is not well standardized within the firearms industry, and threading can vary between manufacturers and models.

For example, factory and aftermarket receivers using the Remington 700 footprint are produced with various types of action threads, all with a 26.99 mm (1+1⁄16 in) diameter, but with a pitch of either a 1.588 mm (16 TPI, Remington standard), 1.411 mm (18 TPI) or 1.270 mm (20 TPI, Savage standard).[2]

Typically, many rifles use thread diameters in the range between 25–27 mm (0.98–1.06 in).[citation needed] Many older rifles from the first half of the 20th century use a thread pitch around 2 mm (12.7 TPI), while many modern rifle use thread pitches around 1.5 mm (16.93 TPI). Fine threaded systems intended for hand tightening typically use thread pitches around 1 mm (25.4 TPI).[citation needed]

Mounting

[edit]

Using action threads to mount a barrel to a receiver typically requires fitting by a competent gunsmith, and typically some machining has to be done.

In this process it is important so set the correct headspace.[3] Correct mounting is important both for safety and accuracy.[4] If the barrel, receiver and bolt are not fitted properly, severe and potential fatal problems can arise due to faulty headspace, e.g. cartridge overpressure and case rupture. Threaded barrels are often mounted to the receiver with a lot of torque, and will therefore generally require tools for assembly and disassembly, such as a suitable action wrench and a vise. Depending on the firearm, a recoil lug is sometimes fitted between the barrel and stock as part of the process,

Cleaning up the receiver and barrel action threads is often done during "blueprinting" in order to increase accuracy.[5]

Action threads

[edit]

List of action threads

[edit]
  • M designates common V threads (like for instance metric threads)
  • Sq designates square threads
  • Tr designates trapezoidal threads
  • The shank length is not always the same at the thread length, which is the case if the insert has a threadless portion (sub-shank)
  • Tenon designates the thread length
  • Shoulder designates the barrel diameter in front of the thread portion
  • Unless otherwise mentioned, right hand threads are assumed. Left hand threads are designated "LH".
Model Diameter (mm) Pitch (mm) Thread angle Shank length Comment Inch
Smith & Wesson J Frame M12.70 0.706 mm 60° Also written as 0.500"-36 1/2"-36
Smith & Wesson K Frame M13.72 0.706 mm 60° Also written as 0.540"-36 69/128"-36
Smith & Wesson L Frame,
Colt J, V,
Colt AA Mark III / King Cobra,
Colt Python (new),
Colt Trooper (J, V, AA) 		M14.27 0.706 mm 60° Also written as 0.562"-36 9/16"-36
Colt Python (old), Colt E & I M14.31 0.794 mm 60° Also written as 0.5634"-32 9/16"-32
Destroyer 1921 carbine (Spanish)[6] M15.88 0.977 mm 60° 15.88 mm 21.59 mm diameter at the shoulder 5/8"-26
Ruger GP-100 M15.88 1.058 mm 60° 5/8"-24
Remington Rolling Block No. 4 Rem. Action (solid frame model)[7]: 33  M16.64 1.588 mm 90° 16.89 mm Also written as 0.655"-16. 21/32"-16
Mathieu[6] Tr16.76 2.54 mm 29° 16.76 mm Trapezoidal threads. Also written as 0.660"-20 85/128"-20
Ruger Blackhawk M16.97 1.058 mm 60° Also written as 0.668"-24 43/64"-24
Smith & Wesson N Frame M17.02 0.706 mm 60° Also written as 0.670"-36 43/64"-36
Remington Rolling Block No. 4 Rem. Action (takedown model)[7]: 33  ⌀17.15 (no threads) N/A 17.02 mm* Also written as 0.675".
*Of which a length of 5.56 mm of the shank has its diameter reduced to 15.62 mm. 		27/40"
Ruger Single Six series M17.26 1.058 mm 60° 87/128"-24
Colt Single Action Army Revolver (third gen)[8] M17.35 1.058 mm 60° 17.75 mm Also written as 0.683"-24. Only 14.43 mm of the shank is threaded. 87/128"-24
Colt Single Action Army Revolver (first and second gen)[8] M17.65 1.270 mm 60° 17.75 mm Also written as 0.695"-20. Only 14.73 mm of the shank is threaded. 89/128"-20
M1917 revolver M17.65 1.270 mm 60° Also written as 0.695"-20 89/128"-20
Ruger Redhawk M19.05 1.270 mm 60° 3/4"-20
Falling Block Works (FBW) Model K [7]: 68  M19.05 1.588 mm 60° 25.15 mm 3/4"-16
Stiller SPF 2500X[9] M19.05 1.588 mm 60° 3/4"-16
BSA Martini Cadet[10][7]: 53  M19.05 1.814 mm 55° 16.74 mm Maximum 25.40 mm shoulder 3/4"-14
Marlin 336, 1895 (.45-70) Sq19.69 2.117 mm 90° 21.59 mm Square threads 0.775"-12
Marlin 1895 (.450) M19.69 2.117 mm 60° 21.59 mm 0.775"-12
Ruger Mini-14 M20.64 1.270 mm 60° 13/16"-20
Colt AR-15 M20.64 1.588 mm 60° The barrel nut thread is M31.75 x 1.411 mm (1-1/4"-18) 13/16"-16
HK416, HK MR223, HK MR556 M21 1.5 mm 60° The barrel nut thread is M32 x 1.5 mm (1.26"-16.93)[citation needed] 0.827"-16.93
Remington Rolling Block No. 2 Rem. Action[7]: 33  Sq21.59 2.117 mm 90° 30.48 mm* Square threads. Also written as 0.850"-12.
*Of which a length of 10.16 mm of the shank has its diameter reduced to 20.45 mm 		17/20"-12
Remington Rolling Block No. 1-1/2 Rem., Sporting Action[7]: 33  Sq21.59 2.117 mm 90° 36.65 mm* Square threads. Also written as 0.850"-12.
*Of which a length of 12.70 mm of the shank has its diameter reduced to 20.32 mm 		17/20"-12
Remington 1867 Navy pistol Sq21.59 2.117 mm 90° Square threads. Also written as 0.850"-12. 17/20"-12
Kimber M/84 M21.43 1.27 mm 60° 27/32"-20
Sako L46/L-46[6] M21.72 1.588 mm 60° 21.46 mm Also written as 0.855"-16. 55/64"-16
Howa 1500 Mini Action[11] M22 1.5 mm 60°
Zastava M85 «Mini Mauser» M22 1.5 mm 60° 0.866"-16.93
Sako L461 M22 1.6 mm[citation needed] 60° 19.40 mm 0.864"-15.87
Mossberg MVP .223[11] M22.23 0.907 mm 60° Also written as 0.875"-28. 7/8"-28
Weatherby Mark V Varmint,

Weatherby Mark V Varmintmaster[6]

M22.23 1.411 mm 60° 16.99 mm 7/8"-18
Cooper Model 22[12] M22.23 1.588 mm 60° 16.26 mm 7/8"-16
Savage Model 1920 Sq22.86 2.117 mm 90° Square threads. Also written as 0.900"-12. 29/32"-12
Browning BPCR, 1885[13] M23.75 1.270 mm 60° 23.37 mm Also written as 0.935"-20. 15/16"-20
Winchester 1885[7]: 20  M23.75 1.588 mm 60° 23.37 mm 15/16"-16
Browning A-Bolt (early),[14]

Browning BBR[15],
Remington 7600

M23.81 1.270 mm 60° 15/16"-20
TAP-174, TAP-375 M24 1.0 mm 60° 19.75±0.05 mm 27.50 mm shoulder 0.945"-25.4
Sako AI/A1[16] (PPC, Vixen) M24 1.5 mm 60° 0.945"-16.93
Jalonen JJ-91[16] M24 1.5 mm 60° 0.945"-16.93
Keppeler[16] M24 1.5 mm 60° 18 mm 0.945"-16.93
Loppo 1,[16] Loppo 2[16] M24 1.5 mm 60° 20 mm 0.945"-16.93
Remington Rolling Block No. 1 Rem., Blackpowder Action[7]: 33  Sq24.77 2.117 mm 90° 36.02 mm* Square threads. Also written as 0.975"-12.
*Of which a length of 10.62 mm of the shank has its diameter reduced to 23.37 mm 		39/40"-12
Mosin-Nagant M91/30 M24.64,
M24.77

M24.89

1.588 mm,
1.588 mm,
1.814 mm 		55/60° 23.88 mm 30.02 mm shoulder. Thread angle varies. 0.970"-16,
0.975"-16,[17]
0.980"-14[6]
MAS M-1936[6] M24.89 1.588 mm 60° 21.46 mm Also written as 0.980"-16. 63/64"-16
Husqvarna 1640, M24.89 2.117 mm 55° 18.16 mm 27.94 mm shoulder. Also written as 0.979"-12. 63/64"-12
Mauser small ring:
Mauser G33/40,[6][18]
Model 93, 94, 95[6]
Swedish m/1896[6] and m/1938[19] 		M25 2.117 mm 55° 18.16 mm /
16.38 mm /
15.88 mm /
16.2+0.2 mm 		24.89 mm major diameter. 27.94 mm shoulder 0.980"-12,[20]
0.993"-12
Krag–Jørgensen, American model[6]
(US Krag-Jørgensen) 		Tr24.89 2.54 mm 29° 19.23 mm Also written as 0.979"-10. Trapezoidal threads, 24.89 mm shoulder 63/64"-10
CZ 527, BRNO FOX M25 1.25 mm 60° Also written as 0.984"-20.32. 1.024"-20.32
Krico 500, 700, M600, M700 M25 1.25 mm 60° 19.85-0.1 mm 28.00-0.05 mm shoulder 0.984"-20.32
Krico M-600, Tradewind 600[6] M25 1.270 mm 60° 20.32 mm 30.35 mm shoulder 0.985"-20
Lebel Berthier 8 mm[6] M25 1.411 mm 55°/60° 25.53 mm 29.21 mm shoulder 0.985"-18
Varberger 717, 757, 777, Kongsberg Lakelander 389, Kongsberg 393 M25 1.5 mm 60° 19.75±0.05 mm 27.50 mm shoulder 0.984"-16.93
Heym SR 21, SR 30 M25 1.5 mm 60° 29.98 mm 29.25 mm shoulder, 5.90 mm loose recoil lug 0.984"-16.93
Nikko Model 7000,[15]
Golden Eagle Model 7000[15] 		M25 1.5 mm 60° 1"-16.03
FR F1 M25 1.5 mm 60° 22 mm
Sako L57 / L-57[6] M25 1.5 mm,
1.588 mm 		60° 21.46 mm 0.984"-16.93,
0.984"-16
Sako L-579,[6] L579 Forester, L61 (early)[6] M25 1.588 mm 60° 22.10 mm 1"-16
Mauser 8 mm (Siamese)[6] M25 1.814 mm 55° 13.08 mm 27.94 mm shoulder 0.990"-14
Husqvarna 1600, 1900, 2000, 8000,[6]
Carl Gustaf 1900,[15] Carl Gustaf 2000 		M25 2.117 mm 55° 19.56 mm 27.94 mm shoulder 0.984"-12
Mauser 89 (Belgian)[6] M25 2.117 mm 55° 19.3 mm 28.32 mm shoulder 0.985"-12
Mauser 88 (German)[6] M25 2.117 mm 55° 18.29 mm 0.986"-12
Mauser Brevex Magnum[6] M25 2.117 mm 55° 19.56 mm 0.988"-12
Mauser 91 (Argentine)[6] M25 2.117 mm 55° 21.46 mm 33.66 mm shoulder 0.986"-12
Mauser 71/84[6] M25 2.117 mm 55° 21.59 mm 26.10 mm shoulder 0.987"-12
Farquharson rifle
(Gibbs, Jeffery, and others) 		M25.07 1.814 mm 55°/60° 22.23 mm Also written as 0.987"-14.
Thread angle varies with production year and manufacturer 		1"-14
Husqvarna RB shotgun, RB M67[6] M25.10 2.117 mm 55°/60° 16 mm 0.988"-12
Kongsberg M60 jakt, M83, M83S, M83SK M25.23 2.117 mm 55° 16.2+0.2 mm Also written as 0.993"-12. Major diameter 25.23-0.2 mm. 1"-12
Krag–Jørgensen, Norwegian model[6] Tr25.30 LH,
Sq26.67 LH 		2.117 mm 90°/29° 19.5+0.3 mm 29+0.1 mm shoulder. Left hand threads.
*Trapezoidal threads on Steyr manufactured actions, also written as 0.996"-12 LH.[21]
*Square threads on Kongsberg manufactured actions, also written as 25.3-0.1 mm.[22] 		1"-12 LH,
1-1/16"-12 LH
Browning A-Bolt (late) M25.40 0.794 mm 60° 1"-32
Mossberg MVP .308,
Mossberg 100ATR,
Mossberg ATR Night Train,
Mossberg 4x4 		M25.40 1.270 mm 60° 1"-20
Remington 788[23] M25.40 1.270 mm 60° 38.1 mm /
39.6 mm 		1"-20
Ruger No. 1,[24] M77,[15][24] M77 MkII[6][25] M25.40 1.588 mm 60° 17.53 mm 35.56 mm shoulder 1"-16
Colt Light Rifle M25.40 1.588 mm 60° 1-16
FN FAL[20] M25.40 1.588 mm 60° 1"-16
Ruger American M25.40 1.588 mm 60° 26.8 mm 1"-16
Ruger American Magnum M25.40 1.588 mm 60° 30.5 mm 1"-16
Ruger Precision Rifle (RPR)[24] M25.40 1.588 mm 60° Timing via barrel nut M31.75x1.411 mm (1-1/4"-18 TPI). 1"-16
Winchester Model 70 (post 64)[6][26] M25.40 1.588 mm 60° 17.78 mm 1"-16
Winchester 54/70 (pre 64)[6] M25.40 1.588 mm 60° 18.8 mm 29.08 mm shoulder 1"-16
Winchester 54/70 (.22 Hornet)[6] M25.40 1.588 mm 60° 21.21 mm 28.96 mm shoulder 1"-16
Tikka M55, M595, M695 M25.40 1.588 mm 60° 1"-16
Tikka T3,[27] T3X M25.40 1.588 mm 60° 22.10 mm 1"-16
Sako L-61 (1. Mod.),

Sako L61R Finnbear (early)

M25.40 1.588 mm 60° 1"-16
Sako 75 M25.40 1.588 mm 60° 1"-16
Sako 85[28] M25.40 1.588 mm 60° 1"-16
SIG Sauer CROSS 60° 1"-16
Lee-Enfield (SMLE)[6] M25.40 1.814 mm 55°/60° 17.46 mm[29] 25.32 mm major diameter. Most have a 60 grader thread angle, but some have 55°. A length of 2.54 mm of the shank at the chamber side in unthreaded with a diameter of 22.86 mm diameter. 1"-14
Homer Koon Omega III[15] M25.40 1.814 mm 60° 1"-14
Champlin[6] (1968, 1971)[15] M25.40 1.814 mm 60° 15.24 mm 1"-14
Martini-Henry, Martini-Enfield,[7]: 63  Metford M25.40 1.814 mm 55°/60° 17.78 mm Thread angle depends on production date 1"-14
Falling Block Works (FBW) Model S [7]: 69  M25.40 1.814 mm 60° 37.97 mm 1"-14
Falling Block Works (FBW) Model H, J [7]: 71  M25.40 1.814 mm 60° 25.15 mm 1"-14
Ranger Arms Texas Magnum[15][6] M25.40 1.814 mm 60° 25.15 mm 29.21 mm shoulder 1"-14
Navy Arms Pedersoli Remington Rolling block[7]: 123  M25.40 1.814 mm 60° 38.86 mm* 30.5 mm shoulder. *The final part of the shank has its diameter reduced to 22.86 mm. 1"-14
M1 Garand, M14, M1A Tr25.40 2.540 mm 29° ACME trapezoidal threads. 24.66 mm-0.13 mm major diameter, 23.19 mm- 0.13 mm minor diameter, 1.32 mm-0.08 mm average thread width. Internal radius of 0.25 mm, external radius of 0.13 mm. 1"-10
(0.968"-10)
Sauer 202 Magnum ⌀__mm N/A N/A Clamp coupling
DPMS G2,
Remington R10 		60° The barrel nut threads are M33.34 x 1.411 mm (1-5/16"-18)
Armalite AR-10,[30]
Eagle Arms AR-10,
Noveske Rifleworks N6 		M25.40 1.588 mm 60° The barrel nut threads are M36.51 x 1.411 mm (1-7⁄16-18, tolerance class 3A). 1"-16
DPMS LR-308[30]
S&W M&P 10,
Bushmaster ORC,
Remington R25,
POF P-308*,
(and most other AR308 / 308AR) 		M25.40 1.588 mm 60° The barrel nut threads are M36.51 x 1.588 mm (1-7/16"-16, tolerance class 2A).
*Tolerance class 2B 		1"-16
Ithaca / Tikka LSA-55[6] M25.91 1.588 mm 60° 1.020"-16
HK417, MR308, MR762 1.5 mm 60° Barrel nut ?-16.93
Sauer 80, 90, 92,
Carl Gustaf 3000,
Colt Sauer[15] 		M26 1.5 mm 60° 1.024"-16.93
Howa 1500,[31][32]
S&W 1500,
Mossberg 1500,
Weatherby Vanguard 		M26 1.5 mm 60° 17.91 mm 3.8 mm depth countersink for the bolt head with a 17.9 mm diameter 1.023"-16.93
Arisaka T99[6] M26 1.5 mm 60° 17.78 mm 31.93 mm shoulder 1.024"-16.93
Remington 799 M26 1.5 mm 60° 1.020"-16.93
Arisaka T38, T44[6][33] M26 1.75 mm 60° 18.29 mm 28.58 mm shoulder 1.024"-14.51
Schultz & Larsen Model S4J,[15] Model 68DL[15] M26 1.8 mm 60° 1.024"-14.11
Steyr-Mannlicher M1895 M26 1.814 mm 60° 17.60 mm 1.023"-14
Springfield M1903 A3/ A4[6] Sq26.42 2.540 mm 29° 18.64 mm Square threads, 29.08 mm shoulder, 26.42 mm major diameter, 25.15 mm minor diameter, 1.30 mm + 0.05 mm average thread width. Also written as 1.040"-10. 1-3/64"-10
The Newton Rifle,[15][clarification needed]

Buffalo Newton 1924[15]

Sq26.42 2.540 mm 90° Square threads 1.040"-10
Sako L61/L-61 (late),
Sako L61R Finnbear (late) 		M26.59 1.588 mm 60° 22.10 mm Also written as 1.046"-16 1-3/64"-16
Remington 700,[2][24] 721, 722, 725,[6][34][35] XP-100, Defiant[24] M26.67 1.588 mm 60° 22.48 mm 30.35 mm shoulder. Also written as 1.050"-16. 1-1/16-16
Remington Rolling Block No. 1 M/1902, 7 mm Action[7]: 33  Sq26.80 2.117 mm 90° 36.32 mm* Square threads. Also written as 1.055"-12.
*Of which a length of 10.92 mm of the shank has its diameter reduced to 25.40 mm 		1-7/128"-12
Remington 783[11] M26.80 0.907 mm 60° Also written as 1.055"-28 1-1/16"-28
Savage Small shank[36][24] (M110, M-110, M110 C, 112)[6][37] M26.80 1.270 mm 60° 42.06 mm Also written as 1.055"-20 1-1/16"-20
Nucleus,[11] Mausingfield[11] M26.80 1.270 mm 60° Also written as 1.055"-20 1-1/16"-20
BAT TR (serienr. over 100)[38] M26.92 1.411 mm 60° 23.37 mm 1-1/16"-18
BAT Bumblebee, Vampire, Igniter[39] M26.92 1.411 mm 60° 19.61 mm 1-1/16"-18
Krag–Jørgensen, Danish model[6] M26.92 2.117 mm 55°/60° 27.43 mm Conical threads 1-1/16"-12
Mannlicher–Schönauer (Greek)[6] M26.92 2.117 mm 60° 18.47 mm Also written as 1.059"-12. 1-1/16"-12
Kongsberg M48 rescue gun M26.92 2.117 mm 55° 18.03 mm Also written as 1.059"-12. 29.85 mm shoulder diameter. 1-1/16"-12
Mauser FÉG 35M, G98/40 M26.92 2.117 mm 55° 18.03 mm 29.85 mm shoulder 1-1/16"-18
Defiance Deviant[40] M26.97 1.588 mm 60° 24.26 mm 3.8 mm depth countersink for the bolt head with a 17.9 mm diameter 1-1/16"-16
HS Precision 2000 Short Action[41] M26.97 1.588 mm 60° 1-1/16"-16
Surgeon 591 Short Action[42] M26.97 1.588 mm 60° 24.13 mm 3.8 mm depth countersink for the bolt head with a 17.9 mm diameter 1-1/16"-16
Thompson/Center Icon[43] M26.97 1.588 mm 60° 1-1/16"-16
Ultimatum Deadline Short Action M26.99 1.270 mm 60° 1-1/16"-20
Kelbly Atlas[44][11] M26.99 1.411 mm 60° 17.58 mm Also written as 1.061"-18 1-1/16"-18
Kelbly Long Atlas[44] M26.99 1.411 mm 60° 14.15 mm 1-1/16"-18
BAT S, SV, B, DS, 3L, 3LL[45] M26.99 1.411 mm 60° 26.7 mm 1-1/16"-18
BAT SB, MB[46] M26.99 1.411 mm 60° 26.7 mm The shoulder must have a radius 1-1/16"-18
Kelbly Atlas Short Action, Atlas Long Action[47] M26.99 1.411 mm 60° 14.15 mm 1-1/16"-18
BAT VR, BTA, TR (TR with serial number below 100)[48] M26.99 1.411 mm 60° 17.68 mm /
19.61 mm 		1-1/16"-18
Stolle Panda Short Action[49] M26.99 1.411 mm 60° 28.32 mm 30 degree countersink for the bolt head 1-1/16"-18
Stolle Panda Long Action[49] M26.99 1.411 mm 60° 24.89 mm Straight bolt head 1-1/16"-18
Curtis Vector[50] M26.99 1.588 mm 60° 1-1/16"-16
Weatherby Mark V, Mark V Magnum[6][51] M26.99 1.588 mm 60° 17.53 mm 1-1/16"-16
Weatherby Mark V Magnum M26.99 1.588 mm 60° 17.78 mm 29.21 mm shoulder 1-1/16"-16
Stiller Predator[52] M26.99 1.588 mm 60° 25.15 mm 3.8 mm depth countersink for the bolt head with a 17.9 mm diameter 1-1/16"-16
Sauer 200, 202,
SIG Sauer 200 STR, 205, 3000,
Carl Gustaf CG 4000 		⌀27 mm N/A N/A 36.5 mm Clamp coupling.[53] The clamping section is 36.5 mm long. The clamping portion of the 202 is somewhat shorter, such that 200 STR barrels can be used in the 202 without modifications (but not necessarily the other way around). 1.063"
Sauer 303 ⌀__mm N/A N/A Clamp coupling.
Sauer 404 ⌀__mm N/A N/A Clamp coupling.
Jalonen JJ-92A[16] M27 1.5 mm 60° 1.062"-16.93
Sardec[16] M27 1.5 mm 60° 25 mm 1.062"-16.93
Sako TRG22, TRG-S, M995, Sako S20 M27 1.5 mm 60° 1.062"-16.93
Carcano M91[6] M27 1.75 mm 60° 27.05 mm 28.83 mm shoulder. Also written as 0.968"-14. 1.062"-14.51
Accuracy International Short action AI
(AT, AX308, AE, AW) 		M27 2.0 mm 60° Indexed via a set screw 1.063"-12.7
Steyr-Mannlicher M1895 M27,

M26.99

2 mm,
2.117 mm 		60° 24.38 mm 1.063-12.7,
1-1/16"-12
Kongsberg M52 (jakt, redningsgevær),
M55 jakt,
M58 skarpskytter,
M59 skarpskytter,
M62 jakt,
M63 selfangstgevær,
M64 treningsgevær,
M67 skarpskytter,
M80 skarpskytter,
M85E 		M28 2.117 mm 55° 16.2+0.2 mm 27.9 mm major diameter. Also written as 1.098"-12. 1.098"-12
Husqvarna 640 M28 2.117 mm 55° 16.2+0.2 mm 1.098"-12
Norinco Model 1887 M28 0.977 mm 60° Clone of Winchester Model 1887 1.100"-26
Savage Bolt Action Shotgun M28 1.270 mm 60° 1.100"-20
Heym SR 10, SR 20,
Mauser 2000, 3000[15] 		M28 2.117 mm 60° 1.100"-12
CZ BBK-02 M28 2.117 mm 60° 1.100"-12
Fabrique Nationale 222 Benchrest[6] M28 2.117 mm 55°/60° 15.9 mm Built on Mauser 98 actions 1.100"-12
Zastava M70 / M98 M28 2.117 mm 55° 1.100"-12
Voere Shikar,[15] K-14[15] M28 2.117 mm 60° 1.100"-12
Mauser large ring:[6][54]

Mauser K98k, M98,[19][24]
Mauser Model 24 (Yugoslavian)[6]
Interarms Mark X[19]

M28 2.117 mm 55° / 60° 16.2+0.2 mm / 15.88 mm Major diameter 27.90-0.10 mm 1.100"-12[20]
CZ 550, 557, 602 M28 2.0 mm 60° 1.102"-12.7
Kongsberg Rolling Block (RB) M/1867 M28 55°
Kongsberg RB shotgun Tr 29° Trapezoidal threads
Jarmann M/1884 55°/60°
Savage Large Shank[36][15][24] M28.58 1.270 mm 60° Also written as 1.120"-20 1-1/8"-20
Savage 110 (short magnum),[6]
Ultimatum Deadline Long Action 		M28.58 1.270 mm 60° 1-1/8"-20
Tubb 2000, Tubb ATR M28.58 1.411 mm 60° Barrel coupler is 1-3/4"-18[55] 1-1/8"-18
Armalite AR-30 M28.58 1.411 mm 60° UNEF, tolerance class 3A 1-1/8"-18
BAT M[56] M28.58 1.588 mm 60° 26.67 mm 1-1/8"-16
BAT HR, BTLA[57] M28.58 1.588 mm 60° 17.30 mm /
19.25 mm 		1-1/8"-16
Herters (BSA) U-9[6] M28.32 2.117 mm 55° 23.37 mm 31.37 mm shoulder. Also written as 1.115"-12. 1-1/8"-12
Falling Block Works (FBW) Model L Express [7]: 72  M28.58 2.117 mm 60° 25.15 mm 1-1/8"-12
Enfield P-14 Tr28.58 2.54 mm 29° 18.29 mm Trapezoidal threads, 33.66 mm shoulder 1-1/8"-10
Enfield 1917[6] Tr28.58 2.54 mm 29° 20.32 mm Trapezoidal threads, 33.66 mm shoulder 1-1/8"-10
Enfield P-14, M1917[6] Sq28.58 2.54 mm 90° Square threads 1-1/8"-10
Remington 30, 30S, 720[6] M28.58 2.54 mm 60° 18.29 mm 33.66 mm shoulder 1-1/8"-10
Accuracy International Long action magnum AI
(AXMC, AX338) 		M30 2.0 mm 60° Indexing via set screw 1.181"-12.7
BAT CT[58] M30.16 1.588 mm 60° 26.42 mm 1-3/16"-16
BAT L[59] M31.75 1.588 mm 60° 44.2 mm 1-1/4"-16
BAT EX with CHEY-TAC breechface[60] M38.10 1.588 mm 60° 37.34 mm 1-1/2"-16
BAT EX with 50 BMG breechface[61] M38.10 1.588 mm 60° 34.80 mm 1-1/2"-16

Alternative methods

[edit]

Several alternative mounting methods to using action threads exist.

Barrel press fit
Pressing the barrel into the receiver to achieve a press fit is an alternative to using action threads which has been used on firearms such as Anschütz Fortner, Anschütz Model 54,[62] AKM[63] and Sauer 101.[64][65]
Barrel nut
Attaching the barrel to the receiver using a barrel nut and a barrel with a shoulder is an alternative to action threads, which has been used in firearms such as the Sten gun and AR-15.
Hand tools
Quick barrel change systems is an increasingly popular alternative, as seen in for example SIG Sauer 200 STR, Roessler Titan or Blaser R8. These methods typically only require simple hand tools (like a hex key) or no tools at all. This can be a great advantage to competition shooters who regularly wear out barrels, or for hunters who want a modular rifle that can shoot several calibers. In these designs, the bolt locks directly into the barrel, and the manufacturer often guarantees that the barrel is headspaced correctly from the factory.
  • A quick change barrel system using threads, intended to be assembled and disassembled without tools.
    A quick change barrel system using threads, intended to be assembled and disassembled without tools.

Muzzle threads

[edit]
Gun with threaded muzzle besides a disassembled muzzle brake and thread protector.

Muzzle threads is one method of fitting accessories such as flash hiders, suppressors or muzzle brakes (compensators). The applicable thread is limited to a certain degree by the bullet caliber and barrel diameter. Right-hand threads (RH) are most common, but left-hand threads (LH) are sometimes used instead. Unless otherwise stated, right-hand threads are usually assumed.

In Europe it has become common to use 1 mm muzzle thread pitches.[66] M14x1 is a common thread type on European hunting barrels, while M18x1 is common on competition bull barrels. A larger barrel thread diameter can improve the precision of the barrel.[67] As of 2021, various Unified threads are still the de facto standard on most American firearms, such as 1/2"-28 (M12.7x0.907) on 5.6 mm (.223") caliber rifles and 5/8"-24 (M15.88x1.058) on 7.62 mm (.308") calibers.

Some common barrel threads are listed below:[68][69][70][71]

Common muzzle threads
Diameter Pitch Comment Inch
M12.7 0.907 mm Common on American rifles and pistols chambered for .223 Rem, .22 LR and 9×19mm. 1/2"-28
M12.7 1.270 mm Common on older European rifles chambered for .22 LR. 1/2"-20
M13.5 1 mm LH Some European 9×19mm pistols 69/128"-25.4 LH
M14 1 mm Very common on European hunting rifles. Also used on some airsoft guns (although often in the left-hand version). 71/128"-25.4
M15.88 1.058 mm Very common on American rifles chambered for the 7.62 caliber (for example .300 BLK, 7.62x39 mm, .308 Win) 5/8"-24
M18 1 mm Common on European rifles with bull barrels. 45/64"-25.4
Less common muzzle threads
Diameter Pitch Comment Inch
M8 0.75 mm Some .22 LR pistols 20/64"-33.87
M9.53 1.058 mm Some .22 LR pistols 3/8-24
M12.7 0.706 mm Some 9 mm rifles 1/2"-36
M13 1 mm Older Glock 9×19mm, Galil (5.56 and 7.62 mm) 33/64"-25.4
M13 1 mm LH Steyr AUG 33/64"-25.4 LH
M14 1 mm LH AK-47 and AKM. Also common on airsoft guns. 71/128"-25.4 LH
M14.29 1.058 mm Some .40"/10 mm pistols. Used on some rifles in .223", 6.5 mm, .308", and 9×19mm. 9/16-24
M14.29 1.058 mm LH FN FAL 9/16-24 LH
M14.68 0.907 mm Some pistols in .45-kaliber. Also written as .578"-28. 74/128"-28
M15 1 mm Some German rifles. 38/64"-25.4
M16 1 mm .45 caliber pistols from HK. 20/32"-25.4
M16 1 mm LH .45 caliber pistols from HK. 20/32"-25.4 LH
M17.46 1.058 mm Some American 7.62 mm bull barrels, as well as some barrels for .450 Bushmaster (11 mm caliber). 11/16-24
M18 1.5 mm Accuracy International .338 LM. 45/64"-16.93
M22 0.75 mm Saiga 12 gauge shotgun 111/128"-33.87
M22.23 1.814 mm Some rifles in 12.7 mm caliber 7/8"-14
M24 1 mm Accuracy International 12.7 mm, Micro Uzi, Uzi pistol 121/128"-25.4
M24 1.5 mm AK-74 (5.45x39 mm) 121/128"-16.93
M25 1 mm Desert Tech 12.7 63/64"-25.4
M25.4 1.814 mm Some rifles in 12.7 mm caliber. 1"-14
M26 1.5 mm Zastava M85 and M92 (7.62x39 mm), Uzi, Mini Uzi. 1-3/128"-16.93

External threads on muzzle accessories

[edit]
Flash hider with external threads for a suppressor on a Zastava M76.

Some accessories, notably suppressors and concussion reduction devices (CRDs), attach via a muzzle device such as a flash hider, compensator, thread protector or sleeve.

External threads on muzzle accessories
Diameter Pitch Comment Inch
M19 1.588 mm Oil filters on Ford, Dodge og Jeep 3/4"-16
M20 2.5 mm Standard metric coarse thread 101/128"-10.16
M20.6 1.588 mm Flash hiders from Kineti-Tech. Oil filters from Chevy and GM. 13/16"-16
M20.6 1.814 mm Standard pipe thread (NPT). 3/4"-14
M22.9 1.058 mm Q Cherry .900"-24
M24 3 mm Standard metric coarse thread 121/128"-8.47
M27 1.5 mm Ase Utra Borelock,
Klärig Engineering BL2,
Uronen Precision 		1-1/16"-25.4
M28.6 2.117 mm Flash hiders from Cyclone, Angel and Demon, some from SilcencerCo, BattleComp 1-1/8"-12
M30 3.5 mm Standard metric coarse thread 1-3/16"-7.26
M34.9 0.907 mm Quietbore Quickie 1-3/8"-28
M34.9 1.058 mm Some suppressor tubes from SilencerCo, Dead Air, Griffin Armament, ODIN Works, Q LLC,
Torrent Suppressors, Area 419, Energetic Armament, YHM, SDTA, Super Precision Concepts,
Plan B, Enfield Rifle Company, Rex Silentium, JK Armament, Ronin Factory,
JMAC Customs, Enduro, ASR, Aklys Defense.[72] 		1-3/8"-24
M36 4 mm Standard metric coarse thread 1-27/64"-6.35
M36.5 1.270 mm Suppressor tubes from SDTAC, Diversified Machine, Super Precision Concepts. Maglite D Cell. 1-7/16"-20
M36.5 1.058 mm Some Diversified Machine suppressors 1-7/16"-24
M38.9 1.058 mm Some Diversified Machine suppressors 1-17/32"-24
M42 4.5 mm Standard metric coarse thread 1-21/32"-5.64
M42.5 1.058 mm Some Diversified Machine suppressors 1-43/64"-24

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Barrel threads

View on Grokipedia
from Grokipedia
Barrel threads are external helical grooves machined into a barrel, either at the chamber end to secure it to the receiver or at the muzzle end to provide a standardized mounting interface for various muzzle devices. Muzzle threads, commonly referred to as threaded barrels, enable the secure installation of accessories such as suppressors, flash hiders, muzzle brakes, and compensators, which can reduce noise, , or muzzle flash during firing. In modern firearms design, barrel threads are typically cut with specific pitches and diameters to ensure compatibility; for example, the common 1/2"-28 thread pattern is widely used on barrels for its balance of strength and fine adjustment. Action-end threads have been used since before the 20th century to attach barrels to receivers, while muzzle threading for devices became widespread in the mid-20th century and gained prominence with the rise of suppressor technology and tactical modifications in the late 20th and early 21st centuries. Threaded barrels are available as factory options on many semi-automatic pistols and rifles, or they can be retrofitted by gunsmiths using lathes to cut precise threads without compromising barrel integrity. Key considerations in threading include material compatibility—such as or barrels—to withstand high pressures and heat, as well as regulatory compliance for secure attachment of suppressors in applicable jurisdictions. Notable variations exist across calibers and firearm types; pistol barrels often feature finer threads like 1/2"-28 or metric M13.5x1 left-hand patterns to accommodate compact designs, while rifle barrels may use coarser 5/8"-24 for larger calibers. Protective thread protectors are frequently included to prevent damage from debris or impacts when no device is attached. Overall, barrel threads enhance versatility, supporting applications in , , and use by allowing modular customization of barrel attachment and muzzle configurations.

Thread Fundamentals

Definition and Purpose

Barrel threads consist of helical ridges machined into the exterior surface of a firearm barrel, enabling secure and removable connections with corresponding threaded components. These threads are typically precision-cut to ensure alignment and structural integrity, distinguishing them from internal rifling which imparts spin to projectiles. The primary purposes of barrel threads are twofold: they allow for the modular attachment of the barrel to the firearm's receiver or action, facilitating disassembly, replacement, and maintenance; and they provide a standardized interface at the muzzle for mounting accessories such as suppressors, flash hiders, muzzle brakes, or compensators. This design promotes versatility in firearm configuration without compromising safety or performance. By enabling precise attachment of muzzle devices, barrel threads offer several key benefits, including enhanced accuracy through reduced muzzle movement and better , effective management to improve shooter control during rapid fire, noise and flash suppression for tactical or applications, and greater customization options to suit specific shooting needs. These advantages have made threaded barrels a standard feature in modern . Barrel threads have been integral to design since before the for action attachments and evolved significantly in the early with the rise of suppressor technology.

Designation and Specifications

Barrel threads are designated using conventions that specify the and pitch, facilitating precise manufacturing and compatibility. In the imperial system, prevalent in the United States, threads are typically named as a of an inch for the major followed by the threads per inch (TPI), such as "1/2-28" for a 0.500-inch with 28 TPI. These often conform to the Unified National Extra Fine (UNEF) series under the (UTS), which defines a symmetrical V-shaped profile with a 60° included thread angle. For example, the 1/2-28 thread has a major ranging from 0.4989 to 0.4924 inches for Class 2A external threads, a pitch of 0.4757 to 0.4720 inches, and a minor up to 0.4564 inches. Metric designations, common in European and international firearms, follow the ISO format "M" followed by the nominal major diameter in millimeters and the pitch in millimeters, such as "M18 × 1.5" for an 18 mm diameter with a 1.5 mm pitch. These adhere to ISO 68-1, which specifies a basic profile with a 60° thread angle, symmetric flanks, and design parameters for general-purpose metric screw threads. Key specifications include the major diameter, pitch diameter (typically offset by half the pitch from the major), and minor diameter, with tolerances ensuring interchangeability; for instance, metric threads maintain a flank angle of 30° per side. Post-2020 updates to metric standards, including refinements in ISO 68-1:2023, emphasize updated basic and design profiles for enhanced precision in fastening applications, including firearms components. Standardization bodies play a critical role in defining these specifications to ensure safety and compatibility. , the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) establishes voluntary standards for barrel threads, such as those for suppressor interfaces, focusing on dimensions like major and pitch diameters to promote reliability and reduce risks from mismatched components; their suppressor thread drawings (revised May 2025), for example, specify Class 2A for external barrel threads and Class 2B for internal sockets. In Europe, the Commission Internationale Permanente (CIP) oversees proof testing and harmonizes standards across member states, incorporating ISO metric threads for muzzle and action interfaces to guarantee interchangeability in regulated firearms. Classes of fit, such as 2A/2B, provide medium tolerance for general use, balancing ease of assembly with strength, while tighter classes like 3A/3B are reserved for high-precision applications.

Action-End Threads

Common Types and Sizes

Barrel threads at the action end have evolved from custom-machined fits in early 20th-century firearms to standardized dimensions that facilitate aftermarket barrel installations and interchangeability. This shift began with manufacturers like Winchester and Remington adopting consistent thread profiles in the mid-1900s, enabling gunsmiths to produce replacement barrels without extensive reworking of the receiver. By the late 20th century, these standards supported the growth of the precision rifle market, with torque specifications typically ranging from 35 to 65 ft-lbs to ensure secure attachment without damaging components. These threads typically follow Unified National (UN) standards per ASME B1.1 for precision and compatibility. Common action-end thread types vary by platform and caliber, with bolt-action rifles often using Unified National (UN) threads around 1-inch diameter for centerfire calibers, while semi-automatic designs like the AR-15 employ finer pitches for the barrel extension. For rimfire calibers such as .22 LR, threads are smaller to match compact actions, typically starting at 1/2-inch major diameter. Larger rifle calibers like generally require threads up to 1-1/16 inches to accommodate the increased shank diameter needed for strength and headspace control. The Remington 700 pattern, widely adopted for short-action centerfire rifles, features a 1-1/16"-16 UN thread with a major of approximately 1.062 inches, suitable for calibers up to .30. This allows for precise headspacing via the barrel's and is torqued to 35-65 ft-lbs during installation. Savage pre-fit barrels use two shank sizes: a small shank at 1-1/16"-20 (major 1.058 inches) for standard actions and a large shank at 1-1/8"-20 (major 1.120 inches) for heavy-recoil models, both with 60-degree thread angles for easy nut installation. Tikka rifles, such as the T3 and T3x series, employ a metric-equivalent 1"-16 UN thread (M25x1.5875 approximate) with a major of 0.994 inches, optimized for lightweight actions in calibers from .22-250 to . The AR-15 platform uses a 13/16"-16 UNF thread on the barrel extension, with a major of 0.998-0.999 inches per mil-spec tolerances, securing the barrel via the upper receiver's barrel nut. actions feature a 1"-16 UN thread with a 1.000-inch major and 0.730-inch tenon length, a design carried over from pre-1964 models to modern variants for reliable bedding in .308 and similar calibers. Newer modular systems, such as the post-2015 SIG Sauer MCX, incorporate proprietary quick-change mechanisms using a taper-lock system for rapid caliber swaps, diverging from traditional tenon styles while maintaining compatibility with AR-pattern accessories.
PlatformThread SpecificationMajor Diameter (inches)Typical CalibersTorque (ft-lbs)
Remington 7001-1/16"-16 UN1.062.223 to .3035-65
Savage (Small Shank)1-1/16"-20 UN1.058.22-250 to .30835-65
Savage (Large Shank)1-1/8"-20 UN1.120.300 Win Mag+35-65
Tikka T3/T3x1"-16 UN (M25x1.5875 equiv.)0.994.22-250 to .30835-65
AR-15 Barrel Extension13/16"-16 UNF0.998-0.9995.56/.22330-50 (extension to receiver)
Winchester Model 701"-16 UN1.000.243 to .30835-65

Attachment Methods and Alternatives

Threaded attachment of barrels to actions typically employs precision-cut threads on the barrel's breech end, secured via a barrel nut or direct shoulder contact against the action's lug. The process begins with the barrel on a to create concentric threads matching the action's specifications, ensuring the bore aligns properly with the chamber. Shims, often thin washers in varying thicknesses (e.g., 0.001" to 0.010"), are inserted between the barrel extension and action face to fine-tune alignment and preload. Installation involves threading the barrel onto by hand, applying anti-seize compound to prevent , and then torquing the barrel nut to manufacturer-recommended values, typically 30-50 ft-lbs for AR-15 patterns, using an to avoid damaging the receiver. Headspacing is verified throughout by inserting a into the chamber with a stripped bolt; the bolt must close fully on the go gauge but not on the no-go gauge, adjusting via shim stack or minor barrel (approximately 1/60th turn for 18 TPI threads to alter headspace by 0.001"). Essential tools include a for initial threading, torque wrenches for consistent tightening, and headspace gauges to confirm safe dimensions. Common errors, such as cross-threading from misalignment, can ruin threads and compromise ; prevention relies on indicating the barrel bore concentric to the spindle within 0.0002" and using thread alignment jigs during installation. Improper headspace risks case ruptures or excessive pressure, potentially causing malfunctions or . Alternative methods eschew threads for more permanent fixes. Press-fit attachments, as in the design, involve greasing the barrel's chamber end and hydraulically pressing it into the front trunnion until the barrel pin notch aligns, followed by pinning to lock it in place; this creates an relying on material expansion for retention. Pinned and welded techniques secure the barrel via through-pins and fillet welds at the joint, enhancing rigidity but requiring specialized equipment for removal. Monolithic integrally suppressed designs, such as those from Suppressed Weapon Systems, machine the suppressor baffles directly into a single-piece barrel blank, eliminating joints for reduced weight and gas leakage while maintaining barrel integrity. Threaded methods excel in modularity, allowing quick barrel swaps for caliber changes or accuracy tuning without specialized presses, though they demand precise to avoid loosening over time. In contrast, press-fit and pinned alternatives provide superior permanence and vibration resistance, ideal for high-volume fire, but sacrifice ease of maintenance and risk loosening if not perfectly fitted; all methods prioritize headspace for safety, as deviations can lead to catastrophic failures like head separation. Since its release in 2014, desktop CNC mills like the Ghost Gunner have democratized custom action threading for home gunsmiths, enabling precise contouring and thread cutting on pre-chambered blanks with CAD-guided programs for actions like the AR-15. Complementing this, 3D-printed jigs and alignment tools—such as bore guides and thread chasers—have emerged to assist amateur machinists in achieving professional tolerances without full access, though metal components remain essential for durability.

Muzzle-End Threads

Standard Configurations

Standard muzzle threads on firearms are predominantly right-hand ( tightening), facilitating secure attachment of suppressors, flash hiders, and muzzle brakes. This configuration aligns with conventional in most designs. However, left-hand threads (counterclockwise tightening) are employed in select applications, particularly on suppressors, to counteract rotational forces from that could otherwise loosen right-hand attachments during firing. For instance, the 1/2×28 thread pitch is a ubiquitous right-hand standard for 5.56mm (.223 ) rifles, including the , enabling compatibility with a wide array of military and accessories. Thread sizes vary by firearm caliber and type to optimize attachment stability and barrel integrity. In pistols chambered for 9mm Luger, the M13.5×1 left-hand metric thread is a common European specification, providing a precise fit for suppressor pistons while leveraging the left-hand direction to resist unscrewing under cyclic recoil. In contrast, U.S.-market 9mm pistols often use the 1/2×28 right-hand imperial thread for broader accessory interchangeability. For rifles in .223/5.56mm, the 1/2×28 right-hand pitch remains standard, supporting lightweight suppressors without excessive barrel protrusion. Shotguns in 12 gauge typically feature the Remington Choke thread pattern—a right-hand metric equivalent to approximately 0.8125×32—for integrating choke tubes or suppressor adapters directly at the muzzle. The Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) provides standardized drawings for suppressor muzzle threads and sockets across various calibers to promote safety and interchangeability. Military applications emphasize , with the U.S. M4 carbine's 1/2×28 right-hand threads serving as a de facto benchmark for 5.56mm platforms in forces, despite the absence of a unified standardization agreement (STANAG) specifically for suppressor muzzle threads. This pitch ensures consistent mounting of tactical devices across allied equipment. Regional variations reflect manufacturing traditions: U.S. designs favor imperial measurements like 1/2×28 and 5/8×24 for calibers up to .30, prioritizing compatibility with domestic suppressors. European firearms, such as the HK G3 , commonly employ metric right-hand threads like 15×1 RH, aligning with ISO standards for and regional accessory ecosystems. These differences necessitate adapters for cross-regional use, but they promote localized optimization in thread strength and alignment.
Firearm TypeCaliber ExampleCommon Thread PitchDirectionNotes
9mm LugerM13.5×1Left-handEuropean standard; recoil-tightening.
9mm Luger1/2×28Right-handU.S. standard; versatile for accessories.
.223/5.56mm1/2×28Right-handMilitary/civilian norm, e.g., M4.
12 gaugeRem Choke (~0.8125×32)Right-handFor chokes/suppressors; interchangeable.
7.62×51mm (HK G3)15×1 RHRight-handMetric for European platforms.

Pitch and Profile Variations

Pitch variations in muzzle threads for firearms are designed to balance compatibility, strength, and manufacturing precision, with finer pitches typically used for smaller calibers to provide more threads for secure attachment under high . For instance, 28 threads per inch (TPI) is common for calibers like , offering a fine pitch that enhances alignment and reduces play in suppressors or muzzle devices. In contrast, coarser pitches such as 24 TPI are employed for larger calibers like .30 caliber rifles, allowing quicker installation while maintaining sufficient engagement for structural integrity. Metric equivalents, such as 1.0 mm pitch (roughly equivalent to 25.4 TPI), are standard in European firearms and adapters, facilitating international compatibility without sacrificing hold strength. Thread profiles for muzzle ends predominantly follow the (UTS), featuring a 60° V-thread angle for optimal load distribution in high-pressure environments. Whitworth profiles, with a 55° angle and rounded roots, are rare in modern designs but persist in some legacy British firearms for their historical vibration-dampening properties. Truncated profiles, which flatten the thread crests to increase , are adapted for extreme high-pressure applications, such as in precision rifles, to prevent deformation under repeated firing cycles. Adaptations like hybrid threads enable multi-caliber barrels by incorporating dual-pitch segments, allowing a single barrel to interface with various muzzle devices across calibers from 5.56 mm to . Quick-detach (QD) mounts often utilize interrupted threads—segments with gaps that permit rotation and locking in under two turns—enhancing field usability while minimizing exposure to hot gases. The choice of pitch and profile is influenced by diameter to prevent baffle strikes in suppressors, where misalignment exceeding 1.5 degrees can cause the to impact internal baffles, potentially destroying . Finer pitches improve concentricity, reducing this risk by ensuring tighter bore alignment. Additionally, profiles with greater flank engagement, such as truncated variants, enhance resistance, minimizing suppressor loosening during sustained fire in tactical scenarios. Since 2023, additive manufacturing has revolutionized custom muzzle threads by enabling tighter tolerances as low as ±0.001 inches, far surpassing traditional limits and allowing bespoke pitches tailored to specific firearm-suppressor pairings without compromising structural integrity. This advancement supports of hybrid designs, significantly reducing production costs for low-volume runs in the firearms industry.

Accessory Threads

Internal Threads on Devices

Internal threads on firearm muzzle devices, such as suppressors and muzzle brakes, are the female threading systems machined into the mounting end of these accessories to securely mate with the external barrel threads. These internal threads are designed to provide a reliable gas seal and structural integrity under high-pressure conditions, typically adhering to Unified National Extra Fine (UNEF) profiles for precision and vibration resistance. The standard fit for these female threads is Class 2B, which offers a medium tolerance that balances ease of assembly with sufficient tightness to prevent gas leakage and ensure alignment, as specified by the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) Z299.6-2025 standard. Common internal thread profiles mirror the corresponding barrel thread pitches but are configured as internal sockets, with examples including 1/2-28 for .223/5.56mm and 9mm applications, and 5/8-24 for .30 rifles. The Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) provides detailed socket drawings for these configurations to promote interchangeability across devices, ensuring that suppressors can be direct-threaded onto compatible barrels without adapters. In direct-thread suppressors, the internal threads fully engage the barrel for a secure, low-profile attachment, while quick-detach (QD) systems may feature shorter or tapered internal threading combined with locking mechanisms for faster mounting. Muzzle brakes and compensators often incorporate similar internal threads with expansion chambers to redirect gases, enhancing control while maintaining compatibility with suppressor mounting. Manufacturing internal threads requires precise to achieve high concentricity with the device's to prevent baffle strikes or misalignment that could damage the accessory or barrel. This alignment is verified using tools like concentricity gauges or range rods inserted through the bore post-threading. For durability in high-heat environments, helical coil inserts (Heli-Coil) may be used in repairs or softer materials to reinforce stripped threads, though direct into harder alloys is preferred for production. Post-2020, the adoption of like and for internal thread components has surged in premium suppressors, offering superior heat resistance and reduced weight; for instance, SIG Sauer's 3D-printed models introduced in 2020 exemplify this trend, with variants providing up to 40% weight savings over while maintaining thread integrity under full-auto fire.

Compatibility and Adapters

Compatibility issues arise primarily from mismatched thread pitches between barrels and suppressor or muzzle devices, such as attempting to attach a 5/8x24-threaded suppressor to a 1/2x28-barreled , which can result in loose connections, cross-threading, and subsequent damage to the barrel or device baffles. This misalignment not only risks thread stripping but also poses hazards like baffle strikes, where the impacts internal suppressor components, potentially causing or accuracy degradation. -specific risks further complicate matters; for instance, using a suppressor rated for .30 on a .223/5.56 barrel may work due to shared 1/2x28 threads, but oversizing the bore without proper verification can lead to gas erosion or incomplete sound suppression. To address these challenges, various adapter types facilitate compatibility, including thread converters that transform pitches like 1/2x28 to 5/8x24, allowing a single suppressor to fit multiple firearms without re-threading the barrel. Spacers extend effective barrel length to accommodate longer devices, while multi-caliber quick-detach (QD) systems, such as those using 1.375x24 HUB threads, enable seamless swaps across calibers from to . SilencerCo's ASR (Active Spring Retention) system exemplifies this, pairing with dedicated flash hiders or muzzle brakes for rapid attachment and broad compatibility across their rifle suppressors like the Hybrid 46M and Omega 36M. Best practices for installation emphasize precise measurement of barrel threads using calipers or thread gauges to confirm pitch and ensure alignment, followed by cleaning threads and applying high-temperature retainers like Rocksett for secure hold without over-torquing. Thread protectors should be used when devices are removed to prevent debris accumulation and damage, and post-installation testing—such as bore-sighting or firing a few rounds—verifies concentricity to avoid baffle strikes. Recommended torque values range from 20 to 30 foot-pounds, depending on the adapter material, to prevent stripping while maintaining retention under recoil. Regarding legal and safety considerations, adapters themselves do not alter the (NFA) compliance of registered suppressors, as they are considered accessories that must preserve the device's original configuration to avoid reclassification or unlawful modification. Exceeding torque limits or using mismatched adapters can compromise structural integrity, potentially leading to unsafe operation, so adherence to manufacturer specifications is essential. The evolution of universal standards like the HUB mount, introduced by in 2014 and expanded through 2025 with new titanium and steel suppressor releases at , has significantly reduced compatibility barriers by standardizing 1.375x24 interfaces across brands.

References

  1. https://www.silencershop.com/blog/threaded-barrel
  2. https://www.silencercentral.com/blog/silencer-common-barrel-thread-patterns/
  3. https://silencerco.com/blog/why-you-should-always-buy-threaded-barrels-for-new-gun/
  4. https://zaffiriprecision.com/blog/threadedbarrels/
  5. https://www.silencercentral.com/blog/attaching-a-suppressor-to-a-non-threaded-barrel/
  6. https://www.silencerco.com/blog/why-you-should-always-buy-threaded-barrels-for-new-gun/
  7. https://redhawkrifles.com/blog/what-is-a-threaded-barrel/
  8. https://saami.org/technical-information/firearm-suppressor-thread-and-socket-drawings/
  9. https://www.engineeringtoolbox.com/unified-screw-threads-unc-unf-d_1809.html
  10. https://saami.org/wp-content/uploads/2025/05/Suppressor-Rimfire-.5-28.pdf
  11. https://www.engineersedge.com/hardware/iso_681_metric_thread_14599.htm
  12. https://www.boltscience.com/pages/ISO68-1-basic-and-design-thread-profiles.htm
  13. https://standards.iteh.ai/catalog/standards/iso/b10ebaee-6a1f-4c00-a09e-c0590d2dd8da/iso-68-1-2023
  14. https://www.americanrifleman.org/content/saami-muzzle-thread-specs-will-promote-safety-reduce-frustrations/
  15. https://bobp.cip-bobp.org/en/tdcc_public
  16. https://cncmachines.com/evolution-gun-barrels-receivers-craftsmanship-cnc-precision
  17. https://www.x-caliber.net/savage-pre-fit
  18. https://preferredbarrelblanks.com/product/tikka-t3-t3x-pre-fit-barrel/
  19. https://rifleshooter.com/2017/04/barreling-a-winchester-model-70-installation-of-a-remington-700-sporter-barrel-on-a-model-70/
  20. https://precisionrifleblog.com/2013/03/22/rifle-screw-torque-settings-specifications/
  21. https://www.shawcustombarrels.com/news/savage-small-shank-vs-large-shank-barrels/473
  22. https://www.practicalmachinist.com/forum/threads/tikka-t3-thread-pattern.225606/
  23. https://www.ar15.com/forums/ar-15/barrel_extension_thread_spec/4-310303/
  24. https://www.scribd.com/doc/296947990/Ar15-Barrel-Extension-New
  25. https://winchestercollector.org/forum/restoration-repair-and-maintenance/help-with-pre-64-model-70-featherweight-barrel-measurements/
  26. https://mansonreamers.com/headspacing-pre-fit-barrels/
  27. https://www.defenseandmunitions.com/article/firearm-headspace-critical-to-safety-dow-gage/
  28. https://www.americanrifleman.org/content/build-your-own-ak-47-part-2-populating-the-barrel/
  29. https://ak-builder.com/index1.php?dispatch=pages.view&page_id=11
  30. https://www.swsrifles.com/
  31. https://www.defensivecarry.com/threads/threaded-vs-press-pin-barrel.50805/
  32. https://threedgearguy.com/
  33. https://www.capitolarmory.com/support/common-thread-pitches.html
  34. https://jkarmament.com/guide-to-barrel-thread-pitches-for-pistols-and-rifles/
  35. https://www.thefirearmblog.com/blog/2019/06/18/thread-pitch-pistols/
  36. https://allenarmstactical.com/general-info/thread-pitches-13-5lh-vs-1-2x28/2019/06/13/
  37. https://jkarmament.com/products/jk-bald-eagle-12ga/
  38. https://sadefensejournal.com/the-23rd-annual-european-small-arms-cannons-symposium/2/
  39. https://www.gunfinder.com/articles/76092
  40. https://hkparts.net/blog/hk-barrel-thread-pitch-guide/
  41. https://precisionarmament.com/blog/how-to-measure-your-muzzle-threads/
  42. https://www.ring-plug-thread-gages.com/ti-bs-Full-Form-vs-Truncated-Modified.htm
  43. https://www.silencershop.com/blog/quick-detach-vs-direct-thread-suppressor
  44. https://www.silencercentral.com/blog/what-is-baffle-strike/
  45. https://www.surefire.com/news/?p=whats-a-baffle-strike
  46. https://www.atomicdefense.com/blogs/news/suppressor-guide-barrel-threads-concentricity-safety
  47. https://www.phillipscorp.com/usa/top-5-reasons-additive-manufacturing-is-the-future-of-firearm-suppressors/
  48. https://www.tacretailer.com/business/additive-manufacturing-is-revolutionizing-the-firearms-industry
  49. https://saami.org/wp-content/uploads/2025/07/SAAMI-Z299.6-202X-Suppressors-Approved-2025-07-30.pdf
  50. https://www.silencerco.com/blog/how-to-attach-a-suppressor/
  51. https://www.youtube.com/watch?v=8ZB_D61-H_Q
  52. https://gundigest.com/gear-ammo/suppressors/suppressor-mounts
  53. https://www.silencershop.com/gun-accessories/suppressor-accessories/mount-systems.html
  54. https://silencerco.com/blog/silencerco-mounting-systems/
  55. https://www.silencercentral.com/blog/how-to-attach-a-suppressor/
  56. https://www-wp.silencercentral.com/wp/wp-content/uploads/2025/03/silent_bandit_suppressor_manual.pdf
  57. https://silencerco.com/blog/so-you-want-to-buy-a-suppressor-silencer-and-nfa-laws/
  58. https://www.silencershop.com/blog/suppressor-hub-mount
  59. https://www.thefirearmblog.com/blog/shot-2025-silencerco-releases-several-new-suppressors-44818717
Add your contribution
Related Hubs
User Avatar
No comments yet.