Handbook for Shooters and Reloaders

[Andy]

I have both volumes of his work and they are well worth while reading. Keep in mind that Mr. Ackley (like Rocky Gibbs) had some commercial interests and many of his claims concerning performance increases from "improving" a cartridge have since been debunked. His claim that straightening the taper on cartridges reduces bolt thrust has possibly generated the most controversy. In fact bolt thrust is a simple product of case head diameter and pressure, having nothing to do with the shape of the case, understanding that in a dry (non-oiled) chamber, the brass grips the chamber walls, and only the unsupported part (the casehead) stretches back against the bolthead. That doesn't mean that less taper and sharper shoulders doesn't decrease brass "flow" (and hence increase brass life), just that the notion of a tapered cartridge "squirting" out of a chamber is a myth.

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[Gibbs505]

I have both volumes of his work and they are well worth while reading. Keep in mind that Mr. Ackley (like Rocky Gibbs) had some commercial interests and many of his claims concerning performance increases from "improving" a cartridge have since been debunked. His claim that straightening the taper on cartridges reduces bolt thrust has possibly generated the most controversy. In fact bolt thrust is a simple product of case head diameter and pressure, having nothing to do with the shape of the case, understanding that in a dry (non-oiled) chamber, the brass grips the chamber walls, and only the unsupported part (the casehead) stretches back against the bolthead. That doesn't mean that less taper and sharper shoulders doesn't decrease brass "flow" (and hence increase brass life), just that the notion of a tapered cartridge "squirting" out of a chamber is a myth.

No completely, consider the Remmington "Jet" 22 cal revolver. That had a tapered case and caused a great deal of problems by backing out of the chamber when fired and jamming the cylinder.

The revolver and cartridge were both dropped.

[John Lawson]

Depends a great deal on what powder and the load used. Obviously, it takes longer for pressure to empty out of a vessel closed on one end to pass through a smaller hole, yet it passes more quickly through a semi-venturi shape. And, recent laboratory tests show that the powder wads up at the mouth of a necked case, creating a delay and resulting in more pressure. The greater the internal pressure, the greater the case stretch can be, if several factors are present.
The half caste putdowns do not consider that Ackley was using powders not available today that had different burning characteristics. And, nobody even will tell you the water capacity of the case being tested; a factor that has a profound effect on pressure peak, time and brass stretch. Very unscientific, but very convenient for an experimenter who is not an expert in internal ballistics to convince an editor, who is a wordsmith, not a gunsmith to print his rant.
I was also going to mention the .22 jet vs the .22 jet improved and some other common cartridges of that pattern.
A few years back, when several powder makers had bad accidents and new sources of the powder were found and marketed, I had to destroy years of tests, since the newer powders were entirely different in respect to the length of time at peak pressure, etc.
Never forget water capacity and that elusive fourth dimension, time.
Incidentally, it was George Leonard Herter who first debated the value of "improved" cases (see his book "Professional Loading"). Although he was an Ordnance officer during WW-II and the inventer of the Garand winter trigger, his sole claim to internal ballistics knowledge was a few visits to FN and conversations with some of the enginers in Belgium. One wonders, if standard products (such as cartridges) are the ultimate, as he purports, why he spent most of his life looking for modifications. And, why he purported to teach American males to auccessfully get along with a woman by self-publishing a book titled "How to Live with a Bitch."