A word of warning on .762 mil ammo, lots of it available from Russia but it is all steel; even the “soft points” are steel, just dipped in lead. Indoor ranges won't let you shoot them.
I just tried out a couple of Tapco 20 round detachable mags this weekend. They functioned perfectly.
Word of warning though:
While in original configuration, the SKS is considered a curio and relic by the BATFE. If you make any changes to parts on the BATFE list, you must put in enough US-made parts to satisfy 922r requirements for imported rifles. Do a web search for “SKS 922r” and you will find several guides for what you can and can’t do.
lot of ranges run by ex American solders do not like you to shoot Russian guns like Dragonov as they were used against them.
But when you show up with a real good one Everyone on the range takes note.
My son did the same thing to a Chicom SKS and created a Jam-o-matic. I brought it back to its original configuration and introduced him to stripper clips and their proper usage. After a bit a practice you can actually reload from a stripper clip as quickly as swapping out a detachable mag. The only advantage to the detachable mag is capacity. That advantage quickly evaporates if you get even one jam per mag.