I got to say, I am impressed with the Rainier barrel. It just keeps shooting better. Very reliable set up. I've shot Wolf, xm193, Fed TRU 55 gr, A.E. 55 gr. and some green tip.
All ran great.
What gets me is the gas port in the Rainier is only .056. Other 7.5" I've built had to have .078.
That makes for less crap in the receiver and should be less hard on the FCG.
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