Over time I think I have tried several detachable metal mags from John Mason to no name brands, from 5 to 40 round. Some work great out of the box and others need work. What I have found with most of the metal mag I have had, they all loosen up over time. From bent lips to broken spot welds ect ect. If you can live with the 20 round look you can not go wrong with tapco, they just work never stop. If you do have a problem they are warrantied for life.......bet ya cant say that about the metal mags.
Many sks rifles need alterations to the stock to use the tapco mags. Bent lips come from inserting the mag with the bolt closed. There is a warning that comes with the tapco mags stating that doing this will cause damage to the mag. The tapco mags are guaranteed for life in the US ( if you don't damage the feed lips ), try sending one back to tapco to get a replacement.
I don't know where ki11ercane gets his metal 30 round magazines but they are exellent quality.


















































