I am currently considering getting some AR COMP powder to try behind some 178 Amax in my Savage .308 10fp with a 20" barrel. After studying Alliant's load charts, it looks as if I may be borderline on enough velocity for supersonic arrival at 1000 yards out of my 20" tube.
My longtime powder behind my 178 Amax bullets has been IMR 4064. It has been very accurate until my particular 8lb lot lost some potency. In the last 2 F-class matches I shot, I noticed that my groups opened up some. After investigation across the chrono, I discovered I was 80 fps slower than what the same load in the same Lapua brass was historically noted for at that temperature. This slowdown took me out of the sweet spot for my barrel. In the past, I have even done my homework on the temperature sensitivity of 4064 by adjusting my charge weight .1gr for every 10 degree F temperature swing from 60 degrees all the way up to 100 degrees in order to maintain my sweet spot velocity. I even tried loading my wintertime charge weight and shot it across the chrono in 80 degree air and was still 50 fps slow.
After determining my remaining 3 lbs of 4064 would be pretty much useless, I finally broke the seal on an 8lb jug of Varget. I did work up a Varget load under my 178 Amaxes which happened to come in at 44.9gr for 2620 fps velocity with a standard deviation of 3.2 for 5 shots. I printed a .322" 5 shot group @100 yards with this Varget load, so it is pretty much equivalent in accuracy as my old 4064 load. The problem is, this new Varget load won't shoot the first 5 shots from a cold barrel this tight like my old 4064 load would. This Varget load seems to prefer a 5 shot barrel warm up before groups tighten up. I find this rather concerning when a tactical setup like mine really should be at its best for at least the first 2 shots. Judging by the Hodgdon burn rate chart, I wonder if Varget may be a little too slow to be optimum in my 20" barrel, being as IMR 4064 is listed as a tad faster burning. This is what has me thinking on trying some AR COMP to get a little faster burn rate for my 20" barrel.
The only thing delaying me from jumping straight into some AR COMP right now is uncertainty of at least making 2580 fps to keep my 178 Amaxes supersonic @1000 yards. Have any of you done some load workups with AR COMP in a 20" barrel for comparison?
My longtime powder behind my 178 Amax bullets has been IMR 4064. It has been very accurate until my particular 8lb lot lost some potency. In the last 2 F-class matches I shot, I noticed that my groups opened up some. After investigation across the chrono, I discovered I was 80 fps slower than what the same load in the same Lapua brass was historically noted for at that temperature. This slowdown took me out of the sweet spot for my barrel. In the past, I have even done my homework on the temperature sensitivity of 4064 by adjusting my charge weight .1gr for every 10 degree F temperature swing from 60 degrees all the way up to 100 degrees in order to maintain my sweet spot velocity. I even tried loading my wintertime charge weight and shot it across the chrono in 80 degree air and was still 50 fps slow.
After determining my remaining 3 lbs of 4064 would be pretty much useless, I finally broke the seal on an 8lb jug of Varget. I did work up a Varget load under my 178 Amaxes which happened to come in at 44.9gr for 2620 fps velocity with a standard deviation of 3.2 for 5 shots. I printed a .322" 5 shot group @100 yards with this Varget load, so it is pretty much equivalent in accuracy as my old 4064 load. The problem is, this new Varget load won't shoot the first 5 shots from a cold barrel this tight like my old 4064 load would. This Varget load seems to prefer a 5 shot barrel warm up before groups tighten up. I find this rather concerning when a tactical setup like mine really should be at its best for at least the first 2 shots. Judging by the Hodgdon burn rate chart, I wonder if Varget may be a little too slow to be optimum in my 20" barrel, being as IMR 4064 is listed as a tad faster burning. This is what has me thinking on trying some AR COMP to get a little faster burn rate for my 20" barrel.
The only thing delaying me from jumping straight into some AR COMP right now is uncertainty of at least making 2580 fps to keep my 178 Amaxes supersonic @1000 yards. Have any of you done some load workups with AR COMP in a 20" barrel for comparison?
