When the 7mmRM came out it had a reputation for wounding and losing smallish(deer size) big game. The cartridge was designed to be a med to big biggame cartridge and bullets were designed accordingly...tough and deep penetrating. 150gr bullets are not designed for light skinned deer but for elk and such.

shoot a lighter bullet, any of the 140's will do better than a 150. Not much difference in weight but a good bit in design.