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Originally Posted by Savage99
Tony,
What happens if there is a "Forward flow of brass" ?
Where does the 'brass' come from?
S99
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You've never seen the ring around brass that shows case head separation? When a case flows it moves from the base up or at least from somewhere on the body forward. On belted magnums it's usually in front of the belt. When you full length resize to move the shoulder back you actually force the brass up the die into the neck, that is why you have to trim. Anyway here is a
link to show you pictures of brass separation.
The removal of body taper and the sharp shoulder actually cause the case flow from being fired to slow down significantly. Case taper and shallow shoulder angles was a leftover byproduct of old style gunpowder that was temperature sensitive. The shape of the case aided in extraction since the tapered body and shoulder reduced the amount of bearing surface on the cartridge if a case happened to be over pressure due to the temperature. Just take a look at the old H&H cartridges and a lot of the old rimmed cartridges and the amount of taper on the bodies and shoulder.
As gun powder became less temperature sensitive you started to see a decrease in taper of the body and shoulder allowing for more powder in shorter cases. By the time P.O. Ackley started doing his research powders were far less temperature sensitive than the old nitro cellulose powder used in the H&H and the first smokeless cartridges. He also claimed that his lack of body taper allowed his cartridges to be ran at higher pressures as well, again because of the bearing surface of the brass on the chamber.