Thread: Velocity Increase During A Shooting Session

Greetings @Bagheera,
I chronographed 42.5 grains of AR2208 with the 140 grain Corelokt in a 7mm-08 recently on my 35P. Velocity was 2,710 fps at 3 metres from a 19 inch barrel. Your result of about 2,750 fps for the same load is in line with this assuming a standard 22 inch barrel. 43 grains, or 0.5 grains increase, should add around 25 fps giving about 2,780.
My first suspicion is barrel fouling in what is a pretty well used barrel with the fouling raising pressures as more shots are fired. Do the various loads, or more importantly the two lots of the 43 grain load make a single group on the target? If they doo then what is the problem? If not it is the first few shots out of the barrel that matter and if these are low due to the velocity you need to zero for them. You will need to test again with your new brass especially if it is a different make but please remember it is the first mag full or part thereof that matters for hunting not what happens after that.
Regards Grandpamac.