AR-10 build/caliber question

[mamboloco]

building a 308 AR-10. to switch to 6.5 all I need is a barrel for that caliber right?

Thanks.

 

[Big Green]

building a 308 AR-10. to switch to 6.5 all I need is a barrel for that caliber right?

Thanks.

New firing pin too. 308 firing pins have been known to pierce primers.

 

[sucker76]

I have a 6.5CM AR10 and the bolt/firing pin is standard. I have never heard of any issues with piercing primers and I haven't seen non 308 firing pins. What is your source?

 

[CyberWolf]

building a 308 AR-10. to switch to 6.5 all I need is a barrel for that caliber right?

Thanks.

You want to make sure the new 6.5CM barrel extention is the same type as the current .308 one to ensure platform/bolt compatibility. I believe the most common is still DPMS (gen 1), but could be something else (e.g. DPMS Gen2, Armalite, etc.).

Also recommended getting a dedicated bbl nut and gas block/tube, unless one-time swap and same gas length.

Finally, be prepared for it to possibly need tweaks to other system components after the switch...

 

[Big Green]

I have a 6.5CM AR10 and the bolt/firing pin is standard. I have never heard of any issues with piercing primers and I haven't seen non 308 firing pins. What is your source?

It appears that isn’t the issue it was thought to be last year. When I was building mine there were some stories of it and some manufacturers changing the firing pins for the 6.5CM. They mostly seem to be interchangeable now. Good to know.

 

[CyberWolf]

New firing pin too. 308 firing pins have been known to pierce primers.

^this is good advice, but would recommend getting a few extra firing pin retaining pins also.

I have a 6.5CM AR10 and the bolt/firing pin is standard. I have never heard of any issues with piercing primers and I haven't seen non 308 firing pins. What is your source?

This is a thing with some setups, my understanding being that it's related to higher operating pressures and more open tolerances.

JP makes both "regular" and "high pressure" .308 bolts (with various carrier options) for this very reason, with the HP Bolt (w/ different HP firing pin) recommended for use with 6.5CM.


fwiw - having worked my way through about a half-dozen varieties of large-frame (.308/6.5) BCGs, far and away the best (for both .308 and 6.5CM) have been the JP FMOS with HP Bolt....

 

[Dawico]

building a 308 AR-10. to switch to 6.5 all I need is a barrel for that caliber right?

Thanks.

Switching once or do you plan to use both barrels?

If using both get another upper.

 

[Ole Cowboy]

Switching once or do you plan to use both barrels?

If using both get another upper.

I am with you, switching bbls brings a can o worms if you are doing it with any kind of regularity. THese rds are too accurate to rotate bbls, just go full fu manchu and have 2 uppers!

Interesting: Running the numbers on 308 vs 6.5 CM at 500 yds: Drop, energy, velocity, so little difference not sure I would invest the coin in both.

 

[mamboloco]

good points, I build two uppers.

not sure what I want to do long term, new to rifles and these ranges. I'll probably just start with the 308 and later on try 6.5 by building the upper.

 

[gshayd]

I built a 6.5 Creedmore AR10. Just make sure the Upper and Lower is compatible and carry on.