I have a question. Are AR-15 7.62x39mm barrels bored to .308 or .310?

[DadSmith]

I can shoot .310 diameter bullets in mine just fine. My nephew said he has shot .308 caliber bullets in his without any drop in accuracy. So this is my question are AR-15 7.62x39mm barrels bored to .308 or .310?

I've emailed several barrel makers I have used but none have responded in over a month.

 

[Greffy]

I am no kind of expert at all, but my guess would be that the barrels are chambered / throated in such a way as to allow for either diameter to be used safely. Might not be a bad idea to send the question to Green Mountain Rifle Barrel Co. or maybe even Palmetto State Armory and ask them the question. Let us know if you do and get an answer.

 

[2in1evtime]

I can shoot .310 diameter bullets in mine just fine. My nephew said he has shot .308 caliber bullets in his without any drop in accuracy. So this is my question are AR-15 7.62x39mm barrels bored to .308 or .310?

I've emailed several barrel makers I have used but none have responded in over a month.

I have wondered why dies for 7.62x39 come with the .308 and .311 sizing -decapping rod myself???

 

[Squid556]

Good question. Especially the one above about the sizing dies… For what it’s worth, I’ve been told the mini 30s are .308 bore. I’m yet to measure an AR 15 barrel personally. I’m guessing they make it close enough that it doesn’t matter.

I know with the 6.5 Carcano, shooting a .264 bullet when you should be shooting .268 shows accuracy degradation. So 4 tho is noticeable but 2 tho probably not.

KAK says they use a “true .311 bore” which makes me feel like other barrel makers are just using .308 to keep thing simple and cheap.

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[DadSmith]

I've got some 125gr Speer TnT bullets. 308 caliber I will try out. Load up 10rds and test them at 50yds.