Can anyone give me max chamber pressuers on the 277 STW or the 25x300 win mag and any other info you may have. I am considering one of the 2 for an upcoming project
.257 STW is based on the 8mm Mag case: max pressure is 65,000 psi
The max pressure for the .300 WM is 64,000 psi. It's a wash there, but the STW holds a lot more powder.