Re: WSSM barrels
The ranges you mention are not practical for AR15 WSSM hunting for anything over small game if fed from the magazine. . The rifles will shoot that far no doubt, but if you were to hunt deer or antelope for example, you would have a problem in the AR15 platform unless you single load the rounds.
The problem is the short magazine length. To get game killing performance at those ranges for deer size animals you have to use heavy bullets, which when seated to magazine length, will consume case capacity and limit the cartridge performance due to less powder. You can do it better with a bolt action with a longer magazine. In the 6.5 WSSM you would need to shoot 140 gr bullets which will consume a lot of the case.
I have the 243 WSSM, 25 WSSM, 6mmAR, 6mmARturbo 40, and the 6 BRX each in and AR15 and would not recommend any for deer beyond around 450 yards.
I have the 300 SAUM in AR10 that will get to around 800 yards if you use the 1000 foot pounds of energy rule.
By the way, 450 yards is still "long range" in my book, even though I have taken deer at over 1,000 yards, but with bigger calibers.