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Thread: Fire-forming Magnum Cases

  1. #1

    Default Fire-forming Magnum Cases

    I am reloading my first magnum. I have heard and read recently about fire-forming Magnum cases before reloading. Does this only apply to new brass? I have assumed that using once fired brass in the same rifle, that the brass would already be formed to that chamber and that adjusting the dies normally would headspace the cartridge on the shoulder.

    Thanks for your help.

    Dan

  2. #2

    Default fireforming new mag brass

    When you buy new brass for your gun, the case is not normally going to be formed to match your gun's chamber. The first time you fire your gun with these cases loaded up with "starter" loads, then they will be properly sized to your gun's chamber. After this first loading, you can neck size your once fired brass so that the length of the case to the shoulder properly fits the chamber. Magnum brass such as .300 Win Mag or 7mm Rem Mag, if full length sized every time you reload it, may only last a few loads, as they are prone to stretch and separate. The .300 Win Mags I have loaded I use only 3 times to make sure the case stays good. Hope this helps.

  3. #3

    Default

    I understand neck sizing for the range, but prefer to full length size for hunting rounds. Is this typically the expected case life for a magnum ? This could get expensive if you shoot a lot! What sort of case life do you get from neck sized brass? When full-length sizing, do you automatically headspace on the belt, or can you adjust the dies to headspace on the shoulder. I read that adjusting your dies can prevent case stretching above the belt which is the cause of short case life in magnums. I have no experience with magnums to know if this is true or not.

    Thanks for your reply.

  4. #4

    Default

    I understand neck sizing for the range, but prefer to full length size for hunting rounds. Is this typically the expected case life for a magnum ? This could get expensive if you shoot a lot! What sort of case life do you get from neck sized brass? When full-length sizing, do you automatically headspace on the belt, or can you adjust the dies to headspace on the shoulder. I read that adjusting your dies can prevent case stretching above the belt which is the cause of short case life in magnums. I have no experience with magnums to know if this is true or not.

    Thanks for your reply.

  5. #5

    Default case life

    I have used both fl sized and neck sized cases for hunting. If you're hunting in hot weather, which I really never have, there might be a problem using neck sized cases, but not necessarily. With necksized cases, I HAVE used magnum cases up to 5 times, that that is the limit for me. I have never been a proponent of belted cases, an old method not really necessary, in my opinion. Belted cases headspace between the front of the belt to the bases of the rim. If the case is neck sized, then the shoulder will be nicely fitted inside the chamber, enhancing accuracy and case life. As far as adjusting the sizing die to increase case life, there is neck sizing and full length sizing. Neck sizing will increase case life somewhat, but there is really no in between sizing.

  6. #6

    Default

    I wouldn't worry too much about neck sizing although I have never done it myself. If you're loading cases to the max you should be able to get about 5 loadings out of them in my experience. You don't really need to load all the way out there. If you're going less than max loads you'll get quite a bit more out of your brass. If you find yourself trimming your brass a lot then you have got a lot of stretching. This is a sign of high pressure of excessive headspace. Both will prematurely kill brass. Load 100-150fps under max loads and your brass will last quite a bit longer. Magnum brass doesn't have a huge life expectancy anyway. If you want to shoot it a lot use minimum loads. I've got 10+ loadings out of my 7mm Rem Mag brass using minimum loads.

  7. #7
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    Default Neck Sizing Belted mags...

    This isn't so much of a case life issue as it is one of catastrophic failure of the brass.

    Neck sizing and NOT pushing the shoulder back will give much better alignment in the chamber for the loaded round and will greatly increase accuracy, with some rifles (Those with sloppy chambers.) and some increase in accuracy in others. It will also increase case life somewhat and of course this depends on the chamber and how sloppy it is. Some rifles will separate cases after two or three firings if full length resized when the chamber is long to the shoulder and the case stretches a lot at each firing.

    The problem is; IF a case separated at firing, (this is a circular cut just forward of the belt that encompasses the case), the high pressure gas can damage the rifle and/or the shooter. It will also likely leave the forward portion of the brass in the rifle chamber. This may be very difficult to get out without tools and certainly will take time away from more important tasks when in the field. Time that could be used to skin the bear rather than the other way around.

    When using full length sizing dies they should be adjusted to fit your rifles chamber. I will say you are doing something in between full length sizing and neck sizing. I guess we could call this "some sizing". This will size the base some but not all the way down and will size the neck completely and just contact the case shoulder, called "bumping the shoulder". This should be done to just move the shoulder back .001"-.002". That's it. Not difficult. This is for brass fired in your rifle not some other rifle. I do all of my belted mag ammo that way for range or field use and I am completely confident that it will work the next time I do it.

    Some rifle chambers are so short to the shoulder thar full length sizing won't even touch the shoulder, they will chamber tight after a couple firings and need to be tossed or the shell holder needs to be shortened. (filed down)

    Case life for high pressure loads is about 5 to 10 firings but when making hunting loads I only use once fired brass that has been fired in the rifle I am loading for, belted mag, standard, ultra or short, all get the same treatment. Or use new brass. The limiting factor for most brass will be the primer pocket stretching and a loose primer fit. I do this by feel when seating new primers, if slightly loose, I shoot this last time, then toss them. Anything that fails before five times had an overpressure load somewhere along the way. A loose primer fit can cause gas leakage around the primer.

    Also there is no problem shooting belted mag ammo for the first time. The brass will stretch for the first but won't stretch on the second firing if the shoulder isn't set back when resizing.


    I hope this clears up the neck vs full sizing of belted cartridges.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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