Finally, a caliber that likes the new ATK AR-Comp powder and a fantastic start to reloading for the LAR-8!
Though narrow in scope, this first range visit after the barrel break-in proved thought provoking and encouraging WRT this rifle.
ATK lists a few recipes on it's web site to this relatively new powder, who's biggest selling point for me, living in Minnesota, is it's temperature stability being boasted as -40 to +160 F. The coldest I've ever deer hunted was -13 F and the hottest range visit in the summer was around +90. I just don't go out when it hotter as it already takes what seems like a lifetime for the barrel to cool between strings. That has gotten better with the advent of a DC powered cage blower with a length of flex hose that fits over the muzzle, that I cobbled up from the junk box. Still, any powder rated for that wide a berth with only 20 fps change, gets my vote. I tried it in my .300 WSSM, but it just didn't pan out as well as Varget and 8208XBR. It did do a reasonably good job in my 6.5 Grendel when shooting 140gr Amax's, but they are heavy for that caliber and Varget still beat it out by a narrow margin. ATK lists 41.7gr for the Amax 168. Not a range of weight, just 41.7gr and they claimed it reaches 2752 fps out of their 24" test barrel with it.
Web site based load data released by the manufacturer tends to be conservative from my experience, so despite normally strting 10% lower, I decided to go with that specific recipe and play with some different primers to see if it had a preference. Boy does it ever! Not the high priced spread though.
Here's a table of the results I obtained using four popular Larger Rifle primers.
Even more fascinating was the 5-shot groups obtained at 100 yards off of a front rest and rear bag, which I shot round robin ala OCW and here's the result:
Now either it loves CCI 200 primers, 2622 fps or both. I've done my share of OCW and OBT experiments and while I can testify from personal experience that they do factor in, I've never seen such a big improvement for 30 caliber bullets in just a 20 fps change from a black rifle
. It wasn't just a good string as I shot these round robin, after 1 fouling shot on another target. I did not dial in the scope to keep everything in perspective.
Once again, as mentioned in my previous Range Report, I got ejector swipes on every shot. Having read up on the issue online, I believe my rifle may be slightly over-gassed. That's something I can improve upon. I've made homebrew Carrier Weight Systems for both my .300 WSSM and 450 Bushmaster on AR15 platforms and the additional 4 oz of weight really makes a difference. Given the additional weight of the .308 BCA, it may take more weight to correct out the dwell issue. That, or I can invest in a variable gas block.
Bottom Line is, I am really impressed by the potential for accuracy. I'm not as happy about the velocity I got versus the factory 24" barrel. 4 inches of difference does not correlate to the difference in velocity. I'm hoping to hit the next node going up in velocity, before I max out the safe chamber pressure. If I can work up .29 MOA accuracy across a range of bullets, I certainly will not continue considering a bull barrel upgrade I mentioned considering in a previous post.
John "Hoot" Hill