If you want to shoot 150gr of T7, get a 52cal LRH with the powerstem breach plug and a 375gr RedHot.....and hold on tight.

Or you can use the Lehigh NFPJ breachplug and 120gr of BH209 and get about the same fps and do it more safely.

Ive shot 120gr BH209 and a 54x50-385gr bullet....it is pretty accurate but not much fun. Recoil is near 458 WinMag levels.