Re: 6/6.5 AR
A. In the 6cal, I am interested in shooting the 105 Berger or 115 DTAC,
Greg Krebaum, Lee Wells, Robert Whitley, and "Bustin" here on the hide build 6m/m rifles that shoot 105 Bergers extremely well and by the way they shoot 87vmax well too...up to 3000 but Bustin's 6m/m runs 105's that fast as I understand it. I shoot 6RAT. This is all in the small chassis AR; An AR15. The 115DTAC is too long to be properly seated in the case to run in the small chassis AR magazine. You'll have to chamber a 243, 6x47 or 6xc for three examples in a large chassis AR's to run 115's and get their benefit.
B. in the 6.5 cal looking at shooting the 140 Berger or 142 SMK.
I would like opinions on caliber choice and why you choose to shoot what you are shooting. Discription of your build might be helpful as well.
Also, do you need to go to a AR10 platform for the 6.5?
Yes. Taking advantage of those heavies will required 260 Rem., 6.5Creedmore, 6.5x47Lapua, and:
an Armalite bolt (because of its right sized firing pin hole),
RL 17 propellant,
Magnum primers (or CCI#41),
adjustable gas block (regulate over-gassing),
OCW load development method (stabilize RL17 but it should be used anyway).
I promise there is a special reason for all these....its a chain reaction. I know.
Built right it works well. This assumes you want to take full advantage of the round. But if you want to merely shoot factory ammo a factory rifle will do. Either way the DTAC bullet is the wat to go. Run it in a 6x47, 243 or 6xc. Get GAP, Madesha, or Sabreco to build it and let us see it when you do. These are all big chassis AR's.
I had a x47 Lapua using DPMS Lr308 receivers. Madesha did the bolt work. Wells built the barrel. Used a Clark Carbon fiber float tube. Giessele trigger. The gun shot .3 until a thug stole it.
My shooting buddy just gotta Grendel. We've loaded 107smk, 123 Hornady, and next 108 Skeenar. I'm impressed with its seemingly inherent accuracy, but its no x47 clearly.