thread size of standard AR-15 barrel

ava8harrierusmc1 · December 26, 2009, 02:40 AM

Hello I have a problem I want to buy new upper for my M4 type AR-15 rifle and i need to know the standard thread size of the barrel so that i can when i order my muzzle break I get the correct size I do remember that i read somewhere that it was 1'2'' by 28 threads for the .223 cal. also is that the same size for 6.8 AR type rifle. Thank you for your assistance with this problem.

DnPRK · December 26, 2009, 05:16 AM

Yes, they are 1/2"x28

ETA: this applies to .223 and 5.56

10-96 · December 26, 2009, 06:45 AM

Not always 1/2"x28... I'll have to do some digging, but I've seen 6.8 bbls with threads in the 9/16" ballpark. I'm pretty sure my RRA is one of the later with the 9/16" ballpark-ish threads.

DnPRK · December 26, 2009, 08:04 PM

Most 6.8s are 5/8"x24.
308s are also 5/8"x24.

December 26, 2009, 02:40 AM	#1
ava8harrierusmc1 Member Join Date: May 18, 2009 Location: Rocklin CA Posts: 15	thread size of standard AR-15 barrel Hello I have a problem I want to buy new upper for my M4 type AR-15 rifle and i need to know the standard thread size of the barrel so that i can when i order my muzzle break I get the correct size I do remember that i read somewhere that it was 1'2'' by 28 threads for the .223 cal. also is that the same size for 6.8 AR type rifle. Thank you for your assistance with this problem. __________________ Life is just to short to be upset by the little things in life. So if something big happens and you don't like it just wait hopefully in the end they will get it in the end if you know what I mean!

December 26, 2009, 05:16 AM	#2
DnPRK Senior Member Join Date: August 25, 2001 Location: LC, Ca Posts: 1,723	Yes, they are 1/2"x28 ETA: this applies to .223 and 5.56 Last edited by DnPRK; December 26, 2009 at 08:04 PM.

December 26, 2009, 06:45 AM	#3
10-96 Senior Member Join Date: October 19, 2005 Location: Tx Panhandle Territory Posts: 2,863	Not always 1/2"x28... I'll have to do some digging, but I've seen 6.8 bbls with threads in the 9/16" ballpark. I'm pretty sure my RRA is one of the later with the 9/16" ballpark-ish threads. __________________ Rednecks... Keeping the woods critter-free since March 2, 1836. (TX Independence Day) I'm going to use the words "clip" and "Long Colt" every chance I get. It grinds my gears to see new members attacked when we all know dang good and well what's being refered to.

December 26, 2009, 08:04 PM	#4
DnPRK Senior Member Join Date: August 25, 2001 Location: LC, Ca Posts: 1,723	Most 6.8s are 5/8"x24. 308s are also 5/8"x24.