Last November I had my first custom bolt gun built. Defiance Deviant Tactical action, 20” proof carbon 1:7 twist barrel, KRG bravo stock. 42.8 gr of H-4350 would put the Berger 80 Vld or 80 eldm in 1/4” to 3/8” 5 shot groups at 100 yards. After about 50 rounds these loads went to 1- 1 1/4” groups. Now I’m having to run 39 gr. H-4350 (3185 FPS) to keep the groups less than 1/2” at 100 yards. Anything hotter and the groups open up to 1 1/4”. I tried with and without suppressor with no real change in group size. I know barrels speed up over time but I didn’t know if accuracy changes like this were normal? Barrel has been cleaned thoroughly and checked with borescope several times to make sure there aren’t any issues with build up. I know the initial loads were perfect on coyotes which resulted in them dropping in place with violent expansion. My concern is that with the 39.0 gr load, I’m not sure the velocity will be high enough to see the rapid expansion that I saw with the 42.8 gr load. So my questions are is it normal to see that a load has to be changed so drastically after the barrel speeds up and does anyone have any experience with these 2 bullets performance at <3200 FPS on game? Thanks in advance
Load currently shooting
Load currently shooting
After 50-75 rounds
Initial testing
Initial testing
Group shot after around 50 rounds below
Load currently shooting
Load currently shooting
After 50-75 rounds
Initial testing
Initial testing
Group shot after around 50 rounds below
Last edited: