There are limitations - Matador Arms Mat-9K 5 inch 9mm Upper Reciever

The buffer less system works as intended, but keep in mind the upper doesn’t have LRBHO. It must be mounted on a lowers such as the Shield Arms SA9 or a Foxtrot Mike 9, they have the LRBHO on them. There in no LRBHO on rhe Aero Precision EPC 9, you can use it but no bolt hold. I had the the same issue with the guide rod bracket breaking, but a call to Matador and a new one was sent to me. Because of this piece I wouldn’t want it to be my primary defense weapon, but with or without a folding brace it makes for a fun range toy.