I know that at least two of the mags I have are USGI. One is an IS and I forget what the other one said. I was just looking at it the other day.

---------- Post added at 02:40 PM ---------- Previous post was at 02:39 PM ----------
Quote Originally Posted by imarangemaster View Post
I have been shooting and carrying M1icon carbines as LEO duty weapons since the early 1980s. I could count the malfunctions in my personally owned and maintained carbines from tens of thousands of rounds on one hand. I SCRUPULOUSLY maintain my weapons, since for 25 years my life depended on them.

1) Make sure recoil spring is close to 10 1/4" long: degraded, short, weak springs can cause malfunctions
2) I have never had a malfunction with a US GI 15 round, and only several through the years with USGI 30s. There are no aftermarket 30s I trust, AT ALL!
3) make sure mag spring is in the right way: /\/\/\/\/\/\/\/\ long side to the rear
4) Make sure it is lubed properly
5) avoid some commercial reloads. BAC makes good ones, as does Georgia Arms. Avoid Aguilla ammo. underpowered, 150 to 200 fps slower than USGI. I use magtech or RP ammo exclusively.
6) a very sloppy trigger housing can cause malfunctions because it holds the magazines aligned with the receiver. I had a firends carbine that did this, DO NOT try to pinch the bottom lugs of the rear of the receiver tighter. They will snap off You can modify the lug on the trigger housing to be tighter.
Can I clarify something in your post here? When you say "long side to the rear" for the mag spring, do you mean the peak should be at the rear?