Hello all, I shot my HK91 copy today it has a Federal Arms Aluminum Reciever and it was great. Was not checking groups just shooting a few rounds to check function and at a 100+ yards it would consistantly hit a milk jug( I know I know....most of us can do that with our 10/22s.) There agian I was checking function more than anything. I see why this design was used so much it rocks!!!!!