1/2"-36 Barrel Threads

[Speed-Freak]

I just got my spiffy new Yankee Hill Machine 7.62x39 AR barrel and am looking for a nice muzzle device to pair with it. The problem I am running in to is the thread size. Standard 5.56 AR is smaller and .308 AR threads are 5/8"-24 standard it seems.

http://yhm.net/index.php?main_page=product_info&cPath=17_29_61&products_id=416

What other firearms use 1/2"-36 to help me find options???

[hermosabeach]

I have never heard of that thread pitch on a rifle.

Have you searched brownells and midwayusa?

[buellster]

Check out CNC Warrior. They have several in that thread. It's not common so your options are limited. You could also use a thread adapter.

http://www.cncwarrior.com/ProductDetails.asp?ProductCode=24841

[ar15barrels]

9mm AR's use 1/2-36 threads.

[VytamenC Tactical]

i have a2 flash suppressors in stock as randall stated they are standard on 9mm and yhm 7.62x 39 barrels

[Whiterabbit]

why not just run a 1/2-36 tap through ANY 1/2-28 muzzle device? Should work just fine, I would think. Tap can not cost more than $25.

[ar15barrels]

why not just run a 1/2-36 tap through ANY 1/2-28 muzzle device? Should work just fine, I would think. Tap can not cost more than $25.

You can do that.
The resulting "Dual Pitch" threads will be missing somewhere between 60% and 75% of their strength for EITHER pitch.

[Whiterabbit]

Figured, and makes perfect sense.

Now, given that many if not most threads are not 100% threads to begin with, we establish that many if not most threads are not as strong as they could be, and that that is OK, it's all just design spec.

So the followup to that would be, do you, Randall, in your professional opinion, believe that losing 75% of its strength is acceptable?

For the sake of simplicity, let's assume we don't need to index the brake/use crush washers. That no washer or a simple lock is all that's needed.

My non-professional opinion is one of confidence that a flash hider would be just fine, and that index-required devices would not be.

[ar15barrels]

So the followup to that would be, do you, Randall, in your professional opinion, believe that losing 75% of its strength is acceptable?

25% of 70% strength is 17.5% strength instead of 70% strength.
I would not find that acceptable.

[CRTguns]

better idea... find an adapter... 1/2x32 inside, 5/8x24 outside. 5/8x24 birdcages are easy to find.

nobody should be cutting 1/2" threads on a .30 cal anyway.

[mocos]

I had a PWS 14mm AK47 brake bored out and threaded for 1/2 x 36 on my colt 7.62 x 39 upper....don't remember if it was 1/2 x 32 or 36.

[kcstott]

better idea... find an adapter... 1/2x32 inside, 5/8x24 outside. 5/8x24 birdcages are easy to find.

nobody should be cutting 1/2" threads on a .30 cal anyway.

Depends on what .30 it is. 7.62x39 in a standard length barrel would be fine but not a 308 or in a shorter barrel the pressure would be too high

[ar15barrels]

I had a PWS 14mm AK47 brake bored out and threaded for 1/2 x 36 on my colt 7.62 x 39 upper....don't remember if it was 1/2 x 32 or 36.

Colt 7.62x39 barrels would come with 1/2-36 threads from Colt.