I just came into a Universal M-1 Carbine in a sliding paratrooper stock. I like this little carbine, but it has some feeding issues. Every few rounds the bullet hits the bottom of the feed ramp and doesn't enter the chamber. The unmarked 30 round mag that came with it has little fore and aft play in the receiver. If I hold the bottom of the mag slightly foward while firing (placing the rounds in a slightly nose up position) it feeds and fires like a champ. Does this sound like a worn out receiver or a cheap mag issue? I have ordered 2 USGI 15 round mags that I am waiting to arrive and am hoping that they will correct this issue. Any thoughts or advice?