Case Head Expansion

Discussion in 'The Ammo & Reloading Forum' started by Guest, Feb 24, 2003.

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    Mauser45
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    (2/15/03 12:11:18 am)
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    Case Head Expansion
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    How much case head expansion is safe for modern rimless cases? I have been loading since back in the seventies but I have always loaded my ammo very conservatively. I have generally just loaded to the "middle" of the loads listed and have seldom had a problem. Of course I always go by the condition of the primer etc. Recently I loaded some ammo until I got .0001-.0002 in. case head expansion and backed off one grain for my max load. According to my nosler book you can load up until you get .0007"-.001" expansion and then back off 1 gr. My loads are very mild according to my load books. Would I get better results using Norma brass instead of Remington? My max load was;
    Rem Brass
    130 Gr. Barnes x
    42.0gr.- IMR 4350
    Fed 210M primer
    Bullets seated to the base of the neck
    At 43.0gr.- 4350, I got .0002 head expansion and the primers were flattened pretty good, yet the book lists up to 45.5 grs. of powder as max. I wish that I had a cronogragh to sort out what velocity I am getting.

    inplanotx
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    Posts: 143
    (2/17/03 12:21:19 pm)
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    Hi Mauser45,
    I think what you want is a case with more area inside to hold more powder. The way I test for cases holding more power (inside room) is to take one case from several manufacturers and block off the primer hole so the case will hold water. You do not want anything absorbent as this would throw off the readings. Fill each case to the top of the neck and then weigh each one. The one with the most water (heaviest) is the one that will hold the most powder.

    Since you did not list the caliber of your reload, I cannot tell what your load looks like in other reloading manuals. I always tell pressure by the primer. When it starts to flatten, I back off about .5 grains.

    You might also want to make a cast of your chamber to see if you may have a tight chamber. Hope this helps.


    Improvise...Adapt...Overcome

    Mauser45
    V.I.P. Member
    Posts: 53
    (2/19/03 11:05:26 pm)
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    Re: Case Head Expansion
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    Thanks inplanotx, I have read about doing a comparison like you describe. I am loading for a 6.5x55 Mauser. I have been assuming that my pressures are up to "full power". Going by several books that I have, my load is about in the middle of the loads listed. I have been getting the same results for the 125 gr. Nosler Partitions. I know that different brands of brass have different capacities but it seems odd that with another brand of brass I could go up (possibly) another 2 grains of powder. This seems like a big discrepancy. As I stated earlier, I usually go by the condition of the primers. Thought that I would try this method and thats why I wanted to find out from others what they considered the Max amount of head expansion.

    rayra
    V.I.P. Member
    Posts: 470
    (2/19/03 11:57:27 pm)
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    I've been reloading for 15yrs+ and have never heard of using 'case head expansion' as a diagnostic indicator of anything but overpressure. Is this an old technique? Or something new?
    If you don't have a cronograph, I'd strongly recommend one to help you with more accurate assessments of your loadings.
    Case-head expansion and primer-flattening aren't the greatest ways to tell what's going on.

    Rich
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