Let's see... 7.62x39mm semi-auto, eh? You must be talking about a SKS, AK, or Mini-30 Ranch.
Using iron sights of the AK/SKS I couldn't shoot a deer with any degree of sportsmanship. But that's just me and U-notch sights. You might be different.
A properly scoped Mini-30 with hunting ammunition might be better suited. I do emphasize properly scoped. I've seen a Mini-14 Ranch rifle "pattern" rather than group due to a poorly fitted scope that embarassingly fell off in the middle of a rifle shooting course.
But I'd rather own a Marlin 1894P over a Ruger Mini-30 or a SKS. I wouldn't mind an AK, but I wouldn't use it for hunting deer.
Just my $0.02