Re: 10 degrees F changes accuracy of load???
Good stuff you've got there! Now go get some H4895, not IMR 4895. I've found TAC and H4895 to give the highest vel w/ big 75-80 gr bullets. Prove to yourself that one is better than the other.
Varget is good for accuracy but it will be hard to put enough into the case to get the vel you want.