I've got a benelli m4 clone and the mag cap retaining pin and spring fell out today when I was disassembling / cleaning my gun. This has never happened before.
I also noticed there is no "entry" hole on the back... so Sulan Arms must've just shoved this in somehow. (It's an sds tac-12.... shoots very well).
I've got pictures but can't figure out how to post/ share...