More Bad Press For The Enfield

[ireload2]

>>>1. The more tapered .303 case presumably puts more pressure on the bolt and receiver than the more parallel-sided 7.62mm case?<<<

Why do you presume that?


>>>Next an action to slice up and measure cross sections<<<

This is not necessary.
Measure it with calipers. Where you have difficulty measure small rectangle and triangles and add their areas. It should take you a whopping 30 minutes.
If you have doubts measure to your best ability. Use an added 10% if you like. Use -10% too. The real number should fall between those values. This is not magic. It is engineering. Close counts like horseshoes, hand grenades and thermonuclear devices.

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[Surpmil]

>>>1. The more tapered .303 case presumably puts more pressure on the bolt and receiver than the more parallel-sided 7.62mm case?<<<

Why do you presume that?

I should rephrase that to say "given an equal case contact area and charge".

I understood it was generally recognized that the more steeply a case tapered, the less adhesion to the chamber walls. Is that not correct?

[Edward Horton]

I should rephrase that to say "given an equal case contact area and charge".

I understood it was generally recognized that the more steeply a case tapered, the less adhesion to the chamber walls. Is that not correct?

Surpmil, you are 100% correct and didn't "presume" anything

.303 Improved Epps

The 303 British suffers from "droopy shoulders". Good in its day, the shallow angle was designed to help in loading and placement of the long stranded propellant "cordite", within the case. While good for factory production then, it's a real problem for the reloader today.

Any cartridge with shallow shoulders is more prone to case stretching, case wall thinning and thickening around the neck. Maximum loads fired from these cases accelerate the process.

Canadian gunsmith Ellwood Epps saw the problem and corrected it. He knew that steeply angled shoulders helped modern spherical and extruded powders burn more within the case and less up the barrel. His solution was to increase the shoulder angle to 35 degrees from 16. At the same time, he decreased the body taper by over 50 thou. The resulting improved cartridge showed a 15 % velocity enhancement over the standard 303 British when fired from the P-14.

After consulting with PO Ackley, Mr Epps reformed the cases with minimal body taper and sharply angled shoulders. Reduced body taper lessens the rearward pressure effects on the bolt and lugs (bolt thrust). Sharp shoulder angles inhibit forward brass flow, which reduces the need to trim cases as often.

Originally, the improvements were made to increase brass life, not to produce a higher velocity round. Mr Epps knew that reshaping the case into a more efficient design would yield this secondary benefit, but considered improved case life to be the most important factor.



303 Epps - Notes on Improved Cases