I have a 1958 era A-5 Light 12-- I'd like to replace the std. magazine cap with the series having the swiveling QD sling clip attaching feature- any good ideas where to find one- used is ok-if the threads are not boogered-- Also, a friend has one like mine, and he claims the design and metallurgy is sufficient that he has fired 3" shells in his without any firing or functioning issues?? Comments?? RWTF