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Thread: Unmodified M3 Mag Usage in MAC/RPB M10/45

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    Unmodified M3 Mag Usage in MAC/RPB M10/45

    Did a bit of searching and found mention, but not really conclusive answer, so figured I'd make an account here and ask the experienced -

    I've got a MAC/RPB doublestamp M10/45 and just recently picked up a batch of 'new in the bag' M3 mags. Knowing something, somewhere would need to be modified, I grabbed a Lage mag catch that's supposed to work with either cobray mags or unmodified m3/gg mags. Catch dropped in and fit perfectly, works fine on my cobray marked mags, but still doesn't seem to want to catch the M3 mags. No biggie - figure a few zips with a file on the first step will fix that, but here's the question - the M3 mags sit noticeably lower in the receiver, which makes sense as the overtravel stops are higher. Even if the mag catch is fitted, do M3 mags run reliably despite not sitting as high up as the cobray marked modified ones?

    Apologies in advance if this has been covered ad nauseum, but I wasn't able to find an answer to that specific bolded question - and everyone tends to address how to run m3 mags a bit differently. Worth noting that my M10/45 runs like a top with the original/cobray mags, and I'm happy to now be part of the community.
    Last edited by tangoprime; 11-19-2020 at 07:20 PM.

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    Here's the difference between the two.

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    Are the new Grease Gun mags USGI or new protection Korean?

    Scott

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    They’re USGI.

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    You've brought up a very interesting question.
    When I started buying M10/45 mags back in the 80's, all the modified (catch step) Greasegun mags also had the insertion stops milled down.
    All ran 100%.
    Years later I bought my first dual mag catch. Nothing was said about the stops, and I don't recall any issues. This was all with open bolt semis. When I bought my first Powder Springs gun I got a bunch of the original MAC modified greasegun mags so I opted to keep the mag catch original. BTW, the MAC mags obviously were done in a jig as you could barely tell. The aftermarket gun show ones usually had grind marks on either side, like Bubba had been busy with a grinder.

    I'm most curious as to some real world shooter feedback on whether the stops make a difference? As an aside, the official story is that MAC made the decision to modify the mags trying for the best of both worlds. The mags would be proprietary and unique to the gun, but no new manufacturing required. Greasegun mags were both plentiful and cheap. Personally I think it was just one more in a series of poor business decisions. Today I'm sure the pitch to the military would be, "Adopt our gun. You already have plenty of magazines for it sitting around doing nothing". Kinda like, "Hey, it takes Glock mags!"
    "All that is necessary for evil to triumph, is for good men to do NOTHING!"
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    I have a Texas Mac that I put the lage catch in, bought 6 gg mags had to file 5 of the 6 to fit, they all fit and run perfectly without doing anything else

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    When you say you filed them, you mean they’re n the rear so they catch, or the overtravel stops on the sides?

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    My M10 didn't come with a magazine. I bought a dual mag catch and unmodified grease gun mags. I had to file the mag catch for it to work, I didn't touch the mag stops. I haven't had a problem with the magazines working.

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    GG work with my JAWS 10/45 as is.

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    I bought a dual mag catch and unmodified grease gun mags. I had to file the mag catch for it to work
    Slaine I'm a bit confused....the whole idea behind the dual mag catch is the ability to use both modified/OEM and unmodified straight Greasegun mags without doing a thing.
    What did you have to modify in order to use the dual catch?
    "All that is necessary for evil to triumph, is for good men to do NOTHING!"
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    Quote Originally Posted by Jack007 View Post
    Slaine I'm a bit confused....the whole idea behind the dual mag catch is the ability to use both modified/OEM and unmodified straight Greasegun mags without doing a thing.
    What did you have to modify in order to use the dual catch?
    Probably just fitted the catch to his mags. Ive had to do this on AK builds too. Some guns I fit the mags, others I fit the mag catch.

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    Registered User timkel's Avatar
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    First, I don't recall reading any reports of problems using an unmodified M3 mags in the M10. There are several aftermarket mag catches available. But this method does present the mag lower in the action.
    Personally I only use modified M3 mags with the original catch. This presents as originally designed. Modifying a M3 mag to M10 specs is a simple job.

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    Personally I only use modified M3 mags with the original catch.
    With original M3, or modified mag stops?
    "All that is necessary for evil to triumph, is for good men to do NOTHING!"
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    Quote Originally Posted by Jack007 View Post
    With original M3, or modified mag stops?
    I take original M3 mags and modify the side mag stops and rear catch area. Just like the original Ingram M10 mags were done.

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    Quote Originally Posted by Jack007 View Post
    Slaine I'm a bit confused....the whole idea behind the dual mag catch is the ability to use both modified/OEM and unmodified straight Greasegun mags without doing a thing.
    What did you have to modify in order to use the dual catch?
    The idea is to be able to use modified or unmodified magazines interchangeably once you have it set up. The grips on macs aren't exactly known for precise manufacturing tolerances. I had to file the catch a little bit to fit it to my gun so it would retain the magazines. I'm sure the catch was designed to on the longer side than what might be necessary because it's easy to file just a little bit off. Adding material if it's too short is a different story.

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    Adding material if it's too short is a different story.
    Ain't that the truth? And no little blue pills can fix it, either! ;-)
    "All that is necessary for evil to triumph, is for good men to do NOTHING!"
    Edmund Burke 1729-1797

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    Registered User timkel's Avatar
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    This is an original Ingram M10 45acp magazine as received with a NIB M10. The pics show the factory Cobray logo and the modifications made to the sides and rear of the mag.



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