I'm sure this has been beaten to death, but this is my first 6.8 AR and I wasn't aware of their issues until after my purchase.  This is the email I sent to M1S and their reply.  Is this true now?  

Hello,
I recently purchased a 6.8 SPC upper with a M1S barrel on it from a guy. Not knowing much about the 6.8 I did some research and found a lot of complaints about the 1:9.5 twist barrels and not being SPC II chamber. Also read about over pressure with the chamber using some ammo. Is there any recommendations as to what I should shoot to get the best accuracy/reliability out of my gun?


Good morning,

Thank you for your interest in our products.

All of our barrels are Spc II Chamber.

Do not hesitate to call us if you have any further questions.

Model 1 Sales

903-546-2087

The newer barrels are SpecII, but the first run of Shaw mfg. barrels years ago were not.

I bought a SpecII reamer and cut a couple, never had an issue with overpressure from the twist rate using commercial ammo.

OK thanks.  How can you tell if it's an early barrel or newer one?

Also what weight of bullet would work best for their twist?  It's a 20" barrel.

Not sure if the markings have changed, but the older barrels are stamped "M1S 6.8mm Rem SPC".

Might check to see if anyone makes a go/no go gauge for the SpecII barrel.

I have been using 110-115gr. Remington and SSA.

It is mainly a leade difference [.05 VS .100] (+/- .014 throat).
Go-no go measures headspace. IIRC- it was a year or 2 ago they changed over.
It will shoot all factory loads except, older Wilson Combat & SSA Tac loads.
SAAMI Spec barrels can be reamed to SPC II with a pull through reamer ( I suggest; done by a trusted gunsmith.).
Reloading manuals all use SAAMI specs. 68forum is about the only (large) source for SPC II reloading.