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How can I tell what thread pitch are on my AR-15 barrel?


A very common question we get here at Veriforce Tactical what are the threads are on my AR-15 barrel.  Well there is a few ways to tell, Here is a list of the most common thread pitches per your Caliber and the likelihood of your AR barrel being these threads:

5.56 – 1/2×28 threads (always)

.223 – 1/2×28 threads (always)

.308 – 5/8×24 threads (always)

7.62×51 – 5/8×24 (always)

.300 blackout – 5/8×24 (usually, but rarely 1/2×28)

6.5 grendel – 5/8×24 (usually, but sometimes 1/2×36 and 9/16×24)

6.5 Creedmoor – 5/8×24 (always)

6.8 SPC – 5/8×24 (always)

.224 Valkyrie – 1/2×28 (always)

9mm – 1/2×36 (usually, but sometimes 1/2×28)

7.62×39 – 5/8×24 (usually, but sometimes 1/2×36)

50 beowulf – 49/64×20 (always)

.458 Socom – 5/8×32 (usually, but sometimes 5/8×24 and rarely 11/16×24)

.450 bushmaster – 11/16×24 (always)

This is a list of NORMAL thread pitches per the caliber, now some manufactures will choose to make an odd ball thread pitch for their barrel.  Thats usually because they will have an abundance of one kind of pre-done muzzle brakes so they make it fit.  Or they just don’t want to spend extra money on new taps or programming.  You should always check with your manufacturer if you can.  If you are in the market for AR-15 muzzle devices check us out for the biggest selection of USA made muzzle brakes and flash hiders with our easy to use product filter to get to your muzzle brake or flash hider faster.

Here is a good way to tell if you think your barrel is 1/2×36, but don’t want to spend money on one just to test.  Most of us have a 5.56/.223 rifle with a flash hider or muzzle brake that is 1/2×28 threads; use it to test the barrel. start to thread it on, you should make it about 1.5 turns before it gets stuck.  If that happens then you should have 1/2×36 threads.  If it goes on all they way, you have 1/2×28 threads.

Why would manufactures threads a .30 caliber bullet with .20 caliber threads pitch?

Usually due to cheapness or ignorance.  The manufacture will have a bunch of 1/2×28 flash hiders lying around, so instead of making/ordering new ones at 1/2×36 (as in the case of 9mm rifles) they will just thread the barrels at 1/2×28 threads.  Its lazy by our standards and CAN be dangerous.

Is it dangerous to thread use .20 caliber threads on .30 caliber bullet?

Yes and no.  If you are using flash hiders then you are fine, they are open at the end and don’t port gasses for muzzle compensation.  Muzzle brakes are dangerous if you have smaller threads.  You cannot use them unless they are drilled out to the proper opening.  In fact in recent years we leave extra space in our opening for just this reason.


21 Comments. Leave new

  • Finally somebody lays it out clearly. Thank you!

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  • What about th 22lr Ar15. Thanks…

    • Most common is 1/2×28, but there are some odd ball manufactures like CZ and Colt that use their own unique threads.

  • Is there a way i can tell the threading on my barrel without any markings?

    • The first number is the outside diameter and the second number is threads per inch. For example, in 1/2″ x 28 the 1/2″ is the outside diameter and the 28 means threads per inch. So it is possible to tell without any markings.

  • funny, my 450 bushmaster is a 5/8×32 , I learned the hard way when I bought a 11/16×24 flash can

  • Scoutdaddy42
    June 10, 2021 3:33 am

    I have been searching for this information for a while now. Thank you very much for explaining the different thread pitches and why they are the way they are!

  • How do you know if it’s 1/2-28 unf or unef?

  • Huge help, this explains it all. Just bought a AR-15 Mini Slip Over Fake Suppressor through you, thank you!

  • I’m building my first AR and recently purchased the V Seven micro brake 1/2 x 28 the opening at the end of the brake looks a little small for 5.56. Is there any thing I can try/ you recommend before firing?

  • Buy a thread gauge at lowes or home depo

  • You guys are the best! Anyone wanting custom firearms work and living in AZ should go to Veriforce!

  • My BCA 450 BM also has a 5/8 x 32 thread.

  • I’m an old shooter, but new to suppressors. I just bought my first can, a Banish 22 for rim-fire applications. Now I’m in the market for something that will fit both a Sig 9mm pistol, a 5.56 rifle, and a 7.62 rifle. But they all have different thread pitches. Between retail costs and DOJ fees, I can’t afford three separate suppressors. Are there silencer thread adapters that would allow me to buy just one suppressor for multiple applications?

    • Absolutely. I’m not converse with the American market, but there must be lots. Just make sure the can has a large enough hole for the biggest round you want to squeeze through it.
      Here in Europe, we have B&T as well as Roedale Precision, just to name two, who both offer an adapter.

      I came here, btw, to decide which thread pattern I was going to cut into my mini 14, in case I buy an AR-15 in order to stick with the same adapter. I also have an 1/2×28 on another rifle, so good news all round.
      Thank you, this was very helpful!

  • Thank you

  • Arthur Benjamins
    December 10, 2023 3:39 pm

    No one said it threads are left-or-right handed.


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