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Thread: difference?

  1. #1

    Question difference?

    Is their any appreciable differences in pressure and speed in a fire formed case over one yet to be fire formed? Also, is there any differences in stretch between a belted and non-belted case?
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  2. #2
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    Yes and the moon effects the pressure a small amount too but I can't measure that either.

    No a belted case doesn't stretch more than a non belted case but if there is a gap between the shoulder of the case and the chamber it will stretch to fill that void. If we full length resize belted case and/or if the chamber is at the upper end in that length to shoulder dimension there will be stretch each time it is fired and eventually it will separate just forward of the belt. This is also true of non belted cases also but there generally just isn't the same amout of slop in non belted chambers as are in belted because the non belted case headspaces on the shoulder. That dimension is an established SAAMI dimension. There is a broad range in min/max, head to shoulder dimensions of a belted case (more slop)because the belted headspaces on the belt not the shoulder.
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  3. #3
    Moderator Paul H's Avatar
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    It depends

    Are you talking a factory chamber, or fire forming in an improved chamber?

    As far as "stretch" in a non belted vs. belted case do you mean in length or diameter? By non belted do you mean rimless or rimmed case? How much a case stretches has more to do with the dimensions of the chamber and the brass than weather or not the case is belted.

  4. #4
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    There can be more expansion fron a new case if it is shot in an oversized chamber.

    A belted case can stretch more if it is undersized as well.


    When reloading to make the case not stretch so much it needs to be resized only enough to permit enough neck tension on the bullet and to permit chambering. This goes for belted or non belted cases. They should be headspaced on the shoulder either way.

    Not sure if this is coming out making any sense or not but each rifle is an individual. A new case may fit perfect and on the flip side if a case is over resized then it may be sloppier than to begin with.

    Any difference...sure.
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  5. #5

    Talking neck sizing

    I personally neck size only with belted or non belted, rimmed or rimless. Once they've formed to the chamber and not sized down, then there's not much expansion, but I was thinking more in line with new cases. Has anyone chronographed a pre-fireformed case and compared it to a fireformed one, standard AND wildcat?
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  6. #6
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    Quote Originally Posted by Murphy View Post
    That dimension is an established SAAMI dimension. There is a broad range in min/max, head to shoulder dimensions of a belted case (more slop)because the belted headspaces on the belt not the shoulder.
    Yup indeedy. You've pointed this out before. Notably, the great difference in shoulder length of Belted Mag. Factory Ammo, before and after it's fired, which can be enough to be scary.

    They wouldn't, (I hope), do it this way if it were a Rimless Cartridge.

    A Rimmed cartridge headspaces on the Rim, like a belted case headspaces SAFELY on the belt.

    At the firing range, I found two 300 Win Mag. cases that were obviously fired in a 300 Weatherby chamber.

    I have another 300 Win Mag case fired in a rifle owned by a friend from long ago, that after firing, doesn't have much neck left. I wouldn't even try to hand-load for such a rifle.

    Methinks that the early Belted Mag, chambers were Too often, Too beeg, in the shoulder length.

    IMO, it's better to neck size, especially with a belted cartridge.

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  7. #7

    Default Yes--sometimes anyway

    I had a friend tell me that my velocity would go up using once fired brass in my rifle as opposed to brand new brass. I did not believe him so I set out to prove him wrong. However, he was right, this particular load in this particular 300 win mag jumped about 50 fps from virgin brass to once fired brass (fired in that rifle). This was also after a full length sizing. So it can make a difference but I would not say it always does.

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