An SKS loaded with 123gr (2350 fps MV) and 150gr (2100 fps MV) bullets has worked on Deer and Bighorn Sheep at ranges out to 250 meters. Proved that it has adequate power with proper shot placement. For larger game I think these loads only have marginal power at best at very close range so I'd be reluctant to try it.
However, my 7.62x39 Ruger No.1 can be safely loaded to well beyond standard ballistics. For example, a 180gr RN bullet does about 2150 fps (using propellant Z

).
Moose hunting was a success this season so I'd like to give my 7.62x39 No.1 with 180gr RN bullets a try next season to see if I can drop a Bull Moose with it called in at close range. Should work with a broadside shot to take out the shoulder and spinal chord. At 50 meters it has the same power as a .30-06 at 200 meters.
7.62x39 Ruger No.1-A with Leupold VX-2 Ultralight 2-7x28mm