M-1 carbines can use 15 or 30 round mags. Your carbine will be able to use the 30 round magazine. The thing to know is it's a good idea to get the M-2 magazine catch, which has an extra "fingerlike" projection to catch the extra tab that is on the rear of the left side of the mag. This will help hold up the extra weight of the 30 rounds. Lack of this catch will not prohibit the use of 30 rnd. mags, but you may find the mag catches on back become distorted.
Also, on some 30 rounders, the follower is shaped to catch the bolt back when it's empty, so don't be surprised if that happens; it's normal. The G.I. 30's have this, the aftermarkets will vary. Some will have the 15 round follower with the ramp the bolt pushes down.
There is no physical difference between the M1 receiver and thee M2 receiver except for the markings. 30 round mags work in either. The key to proper function is the mag catch. It needs to have the side arm to properly support the loaded mag.
One suggestion would be to look for the older (from 5 years or so back) AYP coded 30's----while not USGI, they are/were superb 30 round mags----just as good as any of the USGI's. The only problem is that the second 'round' of AYP's weren't as good as the first----and it's hard (but not necessarily impossible) to tell the difference between them. As I am sure many of the "heavyweights" on the Board will attest----unfortunately----it's getting to the point that the information required to tell the difference bt. the genuine and the 'fake' 30's is approaching the point where it soon will require attendance at a half-day seminar.
AYP mags are suspected to be from Belgium, but we don't have confirmation on that. But the early ones seem to be GI spec and function well. Most of the mags out there are NOT GI. Look for ones marked J, J underlined, KI/M2, AI/M2, and SEY. Those are USGI. The one marked JUST M2 is commercial.
AYP is not USGI. I have read that some may be from Europe, but the ones I have are not that good. I have four of them. Not satisifed at all.
All of the edges are raw cut, as sheared. None of the edges are de-burred as would have been done on a USGI mag. These are marked with a wide impression font, not the thin line font I see on my 15 round USGI mags.
I do have some 30 rounders marked "Made in USA". These are not USGI and I know that, but all edges a de-burred and I have had good service with these. Can't remember who makes them, but a search may bring up that information.
About a year and a half ago I was rummaging around at a gun show in Birch Run Mi. Came across a box of 30 round carbine mags for $10 @. In the bottom of the box there were a half dozen of these. For $10 ,I thought, worth a try and bought two. They had a cosmoline type goo al over then without a mark on them. Did a complete tear down and clean, tweeked the lips to match up with my USGI 15 rounder and they both feed great, not one FFTF. Got lucky I guess. Should have bought more!
I do not remember seeing an SEY marking upside down. That does not mean it could never happen. Production errors occurred.
However with the state of the art of fakery, the only way I would give you an answer is with a hands on inspection of your magazine. Every now and then magazines that were faked from many years ago show up. Since they are no longer around, collectors tend to believe them to be originals.
An inspection is what is needed to compare. A verbal description is impossible to judge.
alright fair enough I mean I don't mind if its usgi or not I just want a reliable magazine is all. from reading around it seems only the usgi ones are reliable thats why i asked but heck if its a repro and it works fine why fret right?? I havn't had a chance to test it at the range yet but quicker to type a post than find time to go to the range I guess .
I have a number of 30 rnders that are reliable, and they aren't USGI issue. I think that it's just a generalization that the GI ones are more reliable. I have seen high cap carbine mags that are poorly made. I have two 40 rounders that are rough around the lips, and the two halves are poorly mated together. In fact, I have not used these because I don't think they are worth tinkering with -- getting the last ten rounds in is a :argh: :!:
I think if the mags look well-made, they're probably worth considering.
But having said that, yes, the general wisdom is USGI will often be best. The others will likely stack up to the degree they have precisely copied the design and fabrication techniques used by the USGI's.
Just my 2 cents.