I have had experience with 30rd steel mags, Tapco 20rd mags, and the standard 10rd box mag that is originally issued on the gun. The 30 rounders tend to jam, and are a haslte to insert. The 20rd tapcos are more reliable, but once again are a pain to insert into the gun. The original 10 round box mag is reliable, and is not hard to insert into the gun (because that is the way it was meat to be, its fixed to the gun, just like the manufatures inteded) if it were me, and the SHTF, i would much rather have a bone stock sks with a bayonette than have some wickid looking black sks with huge clips sticking out of the bottom (they get in the way also). But as the question states, you asked which is more reliable, and i would have to say the 20 rd tapco if you must put one on your rifle