Is the action not cycling far enough back to eject the round? Have you cleaned the gas port? Checked for free movement of the gas piston?
A little more info on the problem would help, simply saying "my gun won't eject" is about as specific as "My car won't start".
As for mags, personally i've never seen as sks function properly with removable mags.
If you want alot of ammo capacity and removable mags, just get an AK-47 variant like the romanian WASR-10 and you'll have two rifles that use the same 7.62x39 ammo.