48 gr of IMR 4895 pushes a 250 gr FMJBT @ 2703 fps out of a 24" barrel (@40,640 psi), very closely replicating M2 Ball. A 39.6 charge would be about 2260 fps (@ 25,159 psi)
I wouldn't count on that cycling reliably. A 47.1 gr charge will give you about 2656 fps and 38,629 psi and should cycle OK.