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Thread: 243 ackley cases

  1. #1

    243 ackley cases

    anybody out there know if the pressure/velocity is different between a case that is being fireformed and one that has been fireformed assuming the same load details

  2. #2
    Yes most definatly it's a hard catridge to read for pressure! I have two of them in the cabinet at the moment and have been shooting this calibre since 2005, I love this calibre but you need a 1-8 twist to see it's full potentional!
    I'm pretty sure you lose a bit of fps fireforming cases I find in most cases you will have same zero fireforming (100 Yds) I'm sure at distance this will be a differnt story! as apposed to your full load even though powder charge could up to 2.5gns less, but using good brass is a must! Stay away from federal it's far to soft and shows pressure signs where a Norma/lapua show none!
    Last edited by Tuck; 18-11-2012 at 23:45.

  3. #3
    Firstly 243 Ackley is a cartridge and not a calibre. .23" or if you like 6mm is the Calibre.

    When choosing a cartridge case to fire form I wonder if people bother to measure the base diameter in front of the extraction groove at the web of the case?

    If you do this you will be surprised that not all makes are actually made to the sized the specification say they should be. Smaller diameter cases will fail and show pressure signs sooner than full sized cases as they have to expand more at the web to fill the chamber even after fire-forming.

    As an example we can look at the measurements of a Remington 280 case I have on the shelf above my desk. It has been formed to 280 AI. The SAAMI specs call these sizes:-

    Rim = 0.473"
    base = 0.470"

    However the case in front of me has these measurements:-

    Rim = 0.466"
    Base = 0.463"

    When you add in the tolerance of the chamber the brass has to move a fair bit to fill it only to then shrink down and often sized down smaller. It's this working of the brass which causes the failures along with brass flow. Although one of the benefits claimed for the Improved case shape is reducing this flow forwards of the brass.

    Strangely enough I have just noticed a R.P 6mm Rem case that I used fro bullet depth checking so it's new sized but has not been fired and the web measures 0.468" so Remington CAN make them right in places if they want too although the rim is still under sized . Conversely checking a fired Bremmer 30-06 case (these are of eastern european origins I understand) the rim measures 0.472" and the web 0.471".

    I have used these cases for reloading for the 30-06 and they appear to be good brass. I acquired them as once fired brass from a fellow club member some years back and they were all fired in one of his Springfield 03 rifles.

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