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Thread: M1 Garand shoulder setback, 0.010" too much for a one time firing?

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    Member tjd308's Avatar
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    M1 Garand shoulder setback, 0.010" too much for a one time firing?

    I know I'll catch hell for not checking from the get go and loading 100 rounds and then realizing my mistake, but admittedly I made an error when full length resizing my brass and set the shoulder back too far and now there is between 0.009 and 0.010" of difference in the shoulder of a fired case and the brass I reformed. This is for an M1icon Garand using mil-surplus Greek HXP brass (30-06 obviously). I know that the standard most use for bolt guns is either to fire form or leave 0.001"-0.002" but autoloaders should be closer to 0.004" to ensure proper chambering.

    *My main question is: Is it safe to shoot this brass this one time to get it back to fire formed size and set my dies properly for the next round of resizing or if I have an unsafe headspace situation that's either dangerous to me or the rifle? Basically will I just be unnecessarily working the brass too much this one time but will be fine or it's not safe and I should just discard the brass?



    Also, I've been using a Hornady headspace gauge using a comparator to see how far the shoulder is set back compared to a fired case. The measurements I get (even on other rounds like a non-fired factory case, fire formed, etc) pretty much all come up below SAAMI spec minimum. From what I've learned, this gauge is meant for comparison purposes only and something like the RCBS precision mic is needed to accurately gauge the distance from the case head to proper datum line on the shoulder (and that the measurements tend to read short for everyone due to the design w/ the beveled soft aluminum edge). The SAAMI min-max difference is 0.007" if I'm reading the SAAMI schematic correctly, but again, the comparator style gauge I'm using makes it seem like I'm well below SAAMI and I'm well below the min (could be in....not sure).

    *Do I even need to worry about SAAMI spec or is measuring relative to a fire formed case all I should worry about? I assume that if I'm using that brass only in the one rifle then it doesn't matter, but if I wanted to make a round that would fit in virtually any chamber that I should then ensure it's inside of the SAAMI min-max, no?

    Sorry for such a long set of questions. I've been hand loading for about two years now and am beyond novice status, but don't want to get careless and do something stupid. I know that excessive an headspace situation (or brass that's out of spec at the shoulder...similar effect) isn't something to be taken lightly. I'd hate to jeopardize my rifle or myself over $50 worth of brass that I should maybe just discarded.


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    Advisory Panel browningautorifle's Avatar
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    Welcome to the forum...

    If you're full length resizing then there's no error to begin with. If you're trying to just neck resize for an autoloader, I think you'll run into problems sooner than later. As for your worries, after you shoot these, you can size them to whatever you like.

    Is this your first attempt at reloading?
    Regards, Jim

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    Use that SAAMI drawing and a little basic arithmetic to see that the acceptable "headspace" difference between a minimum cartridge and a maximum chamber is .0131". So why are you worrying about .010" difference between your fired case (reflecting the chamber dimension) and your sized cartridge cases?

    As you already know, .010" axial play between cartridge and chamber isn't ideal for maximum case longevity. But it hardly represents a hazardous condition. I'm partial to the advice Gen. Hatcher provided on the subject -
    . . . if the headspace is too excessive, the case will be separated or ruptured at a point about 1/2 inch from the head where the thick brass in the base of the case begins to thin out as it joins the walls. When the gun is opened, the base of the cartridge will come out with the extractor, but the forward part of the case will remain wedged in the chamber and the gun cannot be used again until this is removed.

    ". . . With good strong actions and moderate pressure loads, and especially if the shooting glasses are worn, this trouble is not particularly dangerous, but is annoying and inconvenient. Very little, if any, gas escapes to the rear, because the back end of the cartridge, which remains in the chamber, acts as a seal. In fact, it is just such short brass cups that the Germans have for years used as the breech seals in their heavy artillery . . .

    ". . . In my own experimental firing I encountered at least a couple of hundred such separations, and every one of my several thousand students had to experience and correct this situation several times and I never saw enough gas escape to hurt any one. . .

    "Our riflemen are used to measuring the headspace of their rifles by thousandths, and are prone to become very much alarmed if the headspace gauges two or three thousandths of an inch more than the normal maximum. This is a good safe attitude to take, but it is something like measuring cordwood with a micrometer. . ."
    Last edited by Parashooter; 01-08-2017 at 02:51 AM.

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    Member tjd308's Avatar
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    Thanks Jim. Not trying to neck size these...I was just saying I know that's the practice for bolt guns for some, as that's what I do on some of mine.

    As far as my first attempt at reloading, I'm not sure what you're asking. This is once fired factory brass, so my first round of reloading these cartridges. It's not my first attempt at reloading in general. I've been at it about two years now. I've been very meticulous to this point and made the assumption that a full lengthed sized case would be to specs and no worries, but I realized I should be paying more attention to exactly how far I'm setting the shoulders back and it varies even within the recommendations provided in the die instructions. I won't be just mindlessly screwing the die an additional 1/8 to 1/4 turn after hitting the shell holder as RCBS suggests. Like I said in one of my other replies, I'm surprised they are so vague here as this matters. Clearly one should measure how far the shoulder is set back and fine tune the die to suit instead of an "oh well, that's close and ought to do" approach.

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    Advisory Panel browningautorifle's Avatar
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    Quote Originally Posted by tjd308 View Post
    not my first attempt at reloading
    OK then, these rifles aren't known for separating cases. I've shot brass 20 times out of an M1icon and only lost the case because I failed to lube enough once. You can and should FL resize these and not worry, besides .30 cal brass isn't hard to find yet. Not too bad anyway. Trim and FL size and chamfer...all will be well. The only thing about these rifles is...they want the same headstamp and if you can do it lot number. Mixed brass will shoot pieplates and barndoors instead of clean groups.
    Regards, Jim

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    Really Senior Member ireload2's Avatar
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    The Hornady tool has quirk that can mislead you if you try to use it for direct measurements if you want to compare with the SAAMI drawing. More on this later.

    The Hornady tool works fine if you just compare to your fired cases. However the fired cases also vary. Pick 20 to 50 cases and measure all of them. You will find they vary about .002 to .003. This is because the brass temper and the case lengths varied before firing. So find the longest case and verify that it really does chamber in your rifle. Then use that longest case to set the FL die. I set bolt guns used at the range to .000. I set auto loaders .002 shorter. For pumps, lever guns and bolt guns you can determine what you prefer. Ammo used in competition or hunting may be set shorter .001 or .002. Just make sure you check that each setting really works before you load the ammo.

    Ok back to SAAMI.

    The Hornady tool has a little defect. The functional edge of every one of the bushings has had the edge broken (deburred) by hand. This causes an error on every bushing and because the edge break was done by hand every one of the bushings will be different.

    You can get around this if you own head space gages for your rifle.
    (Do not to use a .308 gauge with a .30-06)
    You have to have the exact shoulder angle.
    If you have a .30-06 go gage at 1.940 or 1.942 put the gauge in the Hornady tool and set the dial to the same digits as the gauge length.

    If your gauge says 1.942 the dial caliper should be pointing to exactly 1.942 (or what ever is marked on the gauge. Even a field gauge is ok.
    Then lock the dial and measure your cases. Your caliper will give you the exact number compared to the gauge and it will be accurate within reason compared to the SAAMI drawing. It will not be micrometer accurate but it will be pretty accurate for calipers because your caliper is only going to measure a few thousandths difference.

    Unfortunately you have digital calipers. I don't know how you input a preset number with the digitals. You might have to invest another $20 to get a set that allows inputting the headspace gauge length.


    Try it and if you have any problems send me a PM so we can work through it.
    I think you will find it pretty simple if you have at least one gauge.

    Just remember the shoulder angle of the gauge has to be a perfect match for the round that you are checking.

    You cannot use a 22-250 for a 243 or some other combination like that.

    If you don't have a gauge find someone who does and get your calipers set and measure a case. Mark that case and keep it for a reference instead of using a head space gauge.
















    Quote Originally Posted by tjd308 View Post
    I know I'll catch hell for not checking from the get go and loading 100 rounds and then realizing my mistake, but admittedly I made an error when full length resizing my brass and set the shoulder back too far and now there is between 0.009 and 0.010" of difference in the shoulder of a fired case and the brass I reformed. This is for an M1icon Garand using mil-surplus Greek HXP brass (30-06 obviously). I know that the standard most use for bolt guns is either to fire form or leave 0.001"-0.002" but autoloaders should be closer to 0.004" to ensure proper chambering.

    *My main question is: Is it safe to shoot this brass this one time to get it back to fire formed size and set my dies properly for the next round of resizing or if I have an unsafe headspace situation that's either dangerous to me or the rifle? Basically will I just be unnecessarily working the brass too much this one time but will be fine or it's not safe and I should just discard the brass?

    Also, I've been using a Hornady headspace gauge using a comparator to see how far the shoulder is set back compared to a fired case. The measurements I get (even on other rounds like a non-fired factory case, fire formed, etc) pretty much all come up below SAAMI spec minimum. From what I've learned, this gauge is meant for comparison purposes only and something like the RCBS precision mic is needed to accurately gauge the distance from the case head to proper datum line on the shoulder (and that the measurements tend to read short for everyone due to the design w/ the beveled soft aluminum edge). The SAAMI min-max difference is 0.007" if I'm reading the SAAMI schematic correctly, but again, the comparator style gauge I'm using makes it seem like I'm well below SAAMI and I'm well below the min (could be in....not sure).

    *Do I even need to worry about SAAMI spec or is measuring relative to a fire formed case all I should worry about? I assume that if I'm using that brass only in the one rifle then it doesn't matter, but if I wanted to make a round that would fit in virtually any chamber that I should then ensure it's inside of the SAAMI min-max, no?

    Sorry for such a long set of questions. I've been hand loading for about two years now and am beyond novice status, but don't want to get careless and do something stupid. I know that excessive an headspace situation (or brass that's out of spec at the shoulder...similar effect) isn't something to be taken lightly. I'd hate to jeopardize my rifle or myself over $50 worth of brass that I should maybe just discarded.

    Last edited by ireload2; 03-09-2017 at 10:18 AM.

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