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Old December 21, 2012, 01:01 PM   #24
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Join Date: September 15, 2009
Location: Phoenix, AZ. 30 miles from water, two feet from Hell.
Posts: 355
I remember a test that we would run as a quality assurance for small arms ammo, when I was working at rock island.
It was a test on .45 and 9mm ammo used in current U.S. inventory.
We also had a contract to test “Affect of Manufacturing and Engineering Standards” for the D.O.D
The test was using load cells and strain gauges on selected test ammo in inventory and new manufacturing process.
We first started with the current issue of .45 and then the 9mm both gave the same results, within the caliber of test.
Using new military spec. brass and hard ball ammo, the bullet would be seated up to 240 psi.
Test would start with varying degree of seating pressure of the bullet from a max length each round would support. Current issue magazines would not accept the length of the round.
The bullet would be seated using a load cell and then tested. Seating pressure would have no effect on the V1 or velocity using single based powders. Now the pressure was a different story and we saw all kinds of radicals develop. The bullet would have increasing pressure on the powder.
The other test we would run is the seating strength, which includes the crimp test. A number of bullets would be seated all with the same parameters. A select number rounds would be the “Standard” and the rest tested by firing. The standard would have the bullet seated with different pressure on the crimp and case original dimension. This crimp was also measured by load cell, using Bernoulli Equation and seating coefficient frictional factors.
As the crimp went up in value of tension more radicals did appear V1 and PV3 these did relate into problems with standard deviation and pressure. Due to the decrease of diameter of the bullet, some blow by was noted in extreme cases.
Slight crimping did tend to flatten out the bell curve of V1 and pressure Deltas.
All testing was done with a piston copper crusher type barrels and velocity at a set distance of ten feet for handgun rounds.
The adhesive that was used, back then is a story all unto itself, which I will not get into here.
Some of the newer double based powder acts quite differently when crimped pressure is used, that was after my time.
1. So seating depth has some effect on radicals which can be seen with a chronograph and calculator.
2. Crimping ever so slightly did help.

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