I have the same gun as the OP. And it locks open on the 3rd or 4th magazine I push on the top of the barrel with my finger and it will release. Also sometimes when it slide locks with empty mag. When I take the spent mag oout, and insert a full mag. It will rack a round without my releasing the slide lock. I put a little over 200 rounds through it so far. The place I bought it from told me to bring it back to them and they would take care of it for me.