Sure a Mosin will take deer
I handload for my Mosin, a 1943 Izchevsk 91/30. I use Varget and Hornady's 150 gr. .312 Interlock soft point. My load chronographs at 2860 FPS and shoots a little over MOA. I plan to hunt elk with it this fall in Northern Idaho. Although it is heavy to carry, I have no concerns about the capability of the cartridge. If a .308 will do the job, so will 7.62X54R.