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Thread: Case forming warning

  1. #61
    Boolit Master
    Join Date
    Mar 2010
    NC Arkansas
    Thicker heads mean stronger cases "MAYBE" if the hardness and chemistry of each is equal, but if they differ in hardness or composition further testing is needed to prove the thicker head is stronger. JMHO.
    Spell check doesn't work in Chrome, so if something is spelled wrong, it's just a typo that I missed.

  2. #62
    Boolit Grand Master

    M-Tecs's Avatar
    Join Date
    Apr 2008
    Quote Originally Posted by ulav8r View Post
    Thicker heads mean stronger cases "MAYBE" if the hardness and chemistry of each is equal, but if they differ in hardness or composition further testing is needed to prove the thicker head is stronger. JMHO.
    Yep that would be true. Also stronger is a relatively meaningless term when applied to SAAMI loads and SAAMI cartridges. They may be different in thickness, hardness or alloy composition, however, they are all strong enough for the task at hand.

    Same for the term "safe" they are all safe with SAAMI loads. As to which is more or the most safe that is dependent on the cartridge and chamber/bolt face/firearm design and what unsafe condition is going to induce a failure.

    With unsupported hand gun chambers and some cartridge combinations in coned breech rifle actions a thicker head MIGHT give an additional safety margin to blowing or bulging the unsupported area. Short of that a thicker head offers little or no advantage.

    The term safer is highly dependent on what happens once pressure exceed the case strength. In a rifle like a Remington 700 and a load exceeding 65,000 PSI the primer is the weakest link, next is the primer pocket. As pressures increase the primer will first blank than it will pierce. As pressures go up from there the primer pocket greatly expands and the flashhole is blown out. In this scenario harder case heads would appear to be the "safest" since they would prevent or reduce the amount of gas released into the action from a overpressure load. Having used the AMU V-8 running in the 77,000 to 78,000 PSI harder case heads are "safer" than a softer case head regardless of thickness.

    Once pressure gets higher the case head will pressure weld to the bolt face. On a AR15 type rifle the case head will fail and blow out at the extractor and the extractor will blow out. The barrel may or may not fail at this pressure. On a Rem 700 the fully enclosed bolt face will hold the case head together but the primer pocket expands greatly venting all the gas through the bolt. In both the 700 and AR15 the case will also separate in front of the web at these pressures. What is left of the top of the case is mostly pressure welded to the chamber walls.

    This is based on inspecting a couple of dozen blown or damage rifles.
    Last edited by M-Tecs; 06-02-2020 at 03:50 AM.
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  3. #63
    A lot of the old timers liked to use a chronometer when they became available to incorporate velocity as a check and kept records to note a change.
    Also their loads were cautious " medium" pressure loads to start the record of velocity.
    They usually didn't start with redline tests like I have seen almost universally since the seventies.
    Many new powders available today and l
    think more chances to vary the testing mix.
    Every firearm is a law into itself hasn't changed, even with CNC added to the pot.
    I don't have anything to add to what was posted earlier except that many experimenters and inventors can profit by keeping records, and starting a little lower when starting to load for a cartridge, checking velocity and recording it, then move up in increments and record velocity.
    Any changes made in neck turning, trim length, case capacity, and powder type, lot and grain weight.
    There are more variables too, but if you skip over the basics and just try a Max load without starting low and ramping up, you are like a cave explorer trying to get by without a light .
    Exploring in the dark.
    God Bless all here.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check