300 BO, 6.5 G, or 6 ARC?

[ARlife4me]

I had the same thing happen with my first AR, a M&P15. It was a very basic rifle 5.56 w/ 16" and I think a carbine length gas system.

My 1st AR purchase was a Viking Tactics s&w carbine that uses an A5 recoil system and intermediate gas length. I've had it for 9 or 10 years.