You should not be having any trouble with up to 150 gr bullets if seated to the proper depth. You might want to check and make sure that the brass was sized properly when re-loading. Are you taking all the proper steps for sizing and re-loading, or are you just pulling bullets from factory ammo and replacing? I have used Heavy 200 gr Hornady round-nose bullets with light loads. The Hornadys round-nose bullets have a long taper that starts at the cannelure, so these are a great option for any caliber firearm that you want to load with larger heavier bullets than is normally used for that firearm. However, these bullets will not be MOA...they will serve nicely for 'hunting loads' within 100 yds with 'fair' accuracy. I have loaded them down to 4-5 grs of Red Dot powder and they are extremely quiet.....what I call the 'Poor Man's Whisper'. 6.0 grs is still fairly quiet yet packs a pretty good punch. In fact, this past year, I bought a NEF 7.62x39 barrel for a project gun for experimenting with these kind of loads...works excellent, and I don't have to worry about fouling up my gas-ports in the SKS if I am using heavy cast bullets. 7.62x39 is a great diverse cartridge and can be a lot of fun.
One other thing....I also shoot 7.62x25 pistol, had some 85 gr .308 XTP's and loaded some of these for the SKS, never did get to try them on yotes, but I bet they would be devastating.