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M1A reloading questions

Discussion in 'Handloading and Reloading' started by CSestp, Apr 2, 2012.

  1. CSestp

    CSestp Member

    Oct 9, 2007
    Tulsa, OK
    Hey guys
    after much reading. I have finally gotten ready to do my first reloading. During my reading I found that the M1A is kinda a brass monster, and that all the "preferred" recipes is 41.5 of IMR 4895 with 168 gr using Lake City brass. At least that is kind of the starting point. Here are my questions

    1. If I cant get ahold of Lake City brass how should I start to adjust my powder? less more?

    2. Have heard of people using the same brass (although it was the thicker LC brass) much more than just 3 to 4 times by measuring the headspace in their M1A's and adjusting there overall length to very very close to this. Although it hurts my ego to ask, how do you measure your headspace in your rifle?

    and as always for the dimmer bulbs in the box pictures never ever hurts.
  2. Jimro

    Jimro New Member

    Mar 26, 2012
    Start at 40 grains of 4895 and work up to 41.5 grains just to be sure that it works in your rifle.

    You measure headspace in a couple different ways, but you'll need a caliper, a Wilson cartridge guage, and you can make one of these http://www.gswagner.com/headspacegage/headspacegage.html to measure your chamber.

    Once you record the actual dimensions of your headspace measurement, set up your reloading dies to "bump" the shoulder of the brass back about .001" and you are good usually good to go. Except the M1A really is a monster on brass, and you should full length resize if you plan on using the magazine, for single loads you might get away with "bump sizing" the brass. "Bump sizing" is really only suitable for bolt action, falling block, or break action rifles (and really not so much for the latter two as a lot of people screw it up and have a hard time chambering).

    And reload 4 times and chuck it. The extraction is what causes brass failure in an M1A more than the stress of resizing.

  3. Slamfire

    Slamfire Senior Member

    Dec 29, 2006

    I do not recommend anything but full length sizing for M1a’s/Garands, and I recommend using small base dies.

    Set up your dies with a case gage and size to gage minimum.


    M1a’s, M1 Garands, M1 Carbines, and Mini 14’s all share the same basic bolt firing pin/receiver bridge configuration. On these rifles the firing pin is not retracted until cam down. Prior to then the free floating firing pin is free to wack the primer.

    This is the point at which the firing pin tang engages the receiver bridge. The firing pin is fully forward and able to tap the primer.

    Why this is important is primer sensitivity. If you have an overly sensitive primer the firing pin can tap it with sufficient energy to ignite the thing. If that happens you will either have an in battery slamfire or an out of battery slamfire. These events are very rare, but they happen. I have direct personnal accounts of slamfires in all these mechanisms, except the Mini 14. For that I have a posting from CE Harris claiming slamfires in Mini 14's.

    With a tight case, a long case, the bolt is stopped prior to cam down as it crunch fits the case to the chamber. Given enough tries, with sensitive primers, the occasional M1/M1a has been known to slamfire. Pray it does not happen when the bolt lugs are not engaged.

    This is a slamfire that happened with tight cases


    You should also use the least sensitive primers in this mechanism. I recommend CCI #34’s or the Tula7.62 primers. Both are advertized as being “mil spec”. You absolutely do not want to use Federal Primers as they are the most slamfiring primer on the market. Stay away from any primer that is described as “thin skinned” or “more sensitive”.

    This gentlemen’s experience confirms this:


    For all rounds I recommend you full length resize in a small base die.

    Clean your primer pockets.

    Seat all primers by hand and verify that they are below the case head.

    Use powders in the IMR 4895 burn rate, or use IMR 4895.

    Seat all bullets LT 2.800". I seat my 168's around close to 2.750. You do not want to seat bullets to the lands or any such nonsense which will might delay bolt closure as the bullet is seated.

    Always feed from the magazine. Press single shot loads into the magazine never drop a round in the chamber and drop the bolt on it.
  4. ReloaderFred

    ReloaderFred Senior Member

    Apr 28, 2005
    Oregon Coast
    SlamFire1 gave you good advice. Please heed it.

    I measure headspace in my two M1A's using an average of 5 fired cases in an RCBS Precision Mic. In my M1A Standard, I can close the gas valve and fire a round like a bolt action rifle, manually ejecting the fired round. This gives me an indication of the headspace, without the action ejecting the round. The funny thing is, firing both ways gives me the very same reading in this rifle, contrary to everything I've read about the rifle and what the action does to the brass. I then set my sizing die so the shoulder is set back .003" from the reading of the Precision Mic. My brass lasts longer than 4 or 5 loadings. I get more like 7 or 8 loadings before I scrap the brass for these rifles.

    In my National Match M1A, the gas valve can't be closed, so the readings are taken from brass that has been cycled through the action when fired. The readings are consistant for all 5 cases, using the same components and loading data, so I'm confident that I'm getting a pretty true reading of the chamber.

    I carried the M14 the whole time I was in the Marine Corps. It's an excellent rifle.

    Hope this helps.

  5. P-32

    P-32 Senior Member

    Feb 6, 2005
    the dry side of Washington St
    Is a $.04 cent piece of brass worth damage to your rifle? No, don't go over 3. When I got my 308 M1 back from the gun plumber, he had included instructions stating not to go over 3 reloads with the brass. I figure the plumber who is also a competitor would know what he is talking about. There was no distinction between GI or Commercial. Now I know a M1 Garand is not a M1A, but they are closely related.

    You have gotten some very sound advice. By following advise similar to what is written in this thread, I have not had to suffer a slam fire in any of my service rifle gas guns, 308, ’06 M1 Garands and a couple of AR 15’s.

    The only difference is I use Forester match dies for the 30's.

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