.303 British Maximum cartridge drawing.

[Edward Horton]

45-70 chamber pressures:

Trap Door 1873 Springfield = 18,000 CUP
1886 Winchester & 1895 Marlin = 28,000 CUP
Ruger No.1 & No.3 = 40,000

I didn’t grease my cases or bullets for my 45-70 Ruger No.3 when I was shooting 300 to 500 grain jacketed bullets at 40,000 CUP.

Normal chamber pressure with black powder and the 45-70 is 18,000 CUP or less so case head separations would be a rarity. I never had a 45-70 case head separation in a dry chamber in my No.3 Ruger either.

When I shoot cast bullets my cases are NOT greasy and my lubed bullets are “inside” the case and crimped in place.
(bullet lube sealed inside the case where it belongs)



South African military surplus.



The unfired South African cartridge in a Wilson case gauge (SAAMI chamber) .002 under minimum head space as required. The case rests and is head spacing on its shoulder and not the rim in this gauge. SAAMI cartridge case shoulders should be .002 shorter than minimum head space (even on a rimmed case)



Fired case sticking approximately one eighth of an inch above the SAAMI gauge. This shows how much deeper the military Enfield chamber is compared to SAAMI or CIP chambers.



Brand new Remington case in the Wilson case gauge, the case shoulder is a quarter inch too short and is blown out even further in the military Enfield chamber. (the case should be just .002 below the lip of this gauge)



"So I advise everybody to stop worrying about specifications of arguable origin, validity and applicability, and simply form their real brass to fit their real rifles, not theoretical values. I am intrigued by the theory and the engineering problems that have been thrown up in this thread, but I also want to shoot my rifles!"

Patrick Chadwick


Theoretical and actual are two different things.
Ed Horton