This question has proubly already been asked, but i'm new to the wonderful world of ar's. I have already built the lower and upper parts to the rifle using RRA parts(educational and fun), but now comes the choice of the barrel and ammo combo. I know what will decide this is applications. I plan to have one upper as a 20 inch varmiter for the local coyotes and a 16 in for fun/protection. I also plan to to build and upper or possibly a complete rifle in 6.8 when the ammo becomes more available to hunt the lite skin deer of centrel texas. Any sage advice is welcome and thank you in advance.

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