Back in the day.... There used to be a company which made 30-round, detachable, Zytel NON-DUCKBILL magazines. This was available with a conversion kit which consisted of a Zytel wedge with a lug which was supposed to be screwed to the receiver to retain the front of the magazine.
I bought one of these kits but rather than drill & tap the receiver I modified the wedge and Nylon/Zytel stock so that the wedge was pinned inside the stock and held tightly against the receiver. I never had any issues with this set up. The SKS ran just fine using these 30 round magazines.
Does anybody know if these are still available? Does anybody here have - or have you seen - one of these SKS's which was modified for this set up?