OK, Ted, does this mean my flats of “low brass” might be suspect ?
Well, yea.
I don’t test ammunition, but, in casual conversation with a few production people employed at Federal Cartridge, right up the road from me, promotional ammunition is the most inconsistent and features some of the highest pressures. How inconsistent, and how high pressure, is known by a lot fewer people than you would think.
Best,
Ted
I agree completely with Ted on this.
To push a hypothetical load of 1 1/4 oz. of shot to a desired velocity of 1220 fps requires a certain amount of pressure sustained for a certain time interval. Very different pressure curves with very different peak pressures can accomplish the same goal by utilizing different powders with different burning rates. For simplicity, I'm assuming all else (case, wad, primer, crimp, barrel length, etc) remains equal. A very fast burning powder is going to produce a higher peak pressure, earlier in the curve, to push a charge of shot to that hypothetical 1220 fps velocity. Naturally, the pressure will drop off faster than with a more progressive burning powder. Brisance of the primer is another big variable. I was very surprised to learn some years ago how much a simple change of primers can increase or decrease pressures, even though I knew some unknown difference was likely. Thankfully, GLS posted some testing results on the subject from Tom Armrest that detailed the risks in changing components.
So if a manufacturer of low brass promo ammo can achieve a certain desired velocity with 2 or 3 grains less powder by using a cheaper faster burning powder, it is likely they will do so to maximize profits. Using a few more grains of powder may mean little to those of us who load just enough for hunting. But it really adds up when you are loading millions of shells, and trying to please shareholders.
We've read and heard for years that "Low Brass does not mean Low Pressure." Supposedly, that statement has been tested for accuracy, but I have not seen those test results. Several years ago, I suggested that those of us who are interested could pool resources, and donate to a collective fund, and send a representative array of loads to someone like Tom Armbrust... knowing the data collected would only be good for a particular lot of ammo. Nobody seemed interested, so until something changes, we are going to be stuck with hearsay, second-hand info, conjecture, myths, and be cursed with seeing pressure data for powders that became obsolete when your grandfather was a young lad.
