1941 Winchester .303

[Alan de Enfield]

Question: Is commercial .303 from the UK and Common Wealth countries thin compared to that countries .303 military?

In the UK I think the most common, non US, commercial 303 is Prvi Partisan (PPU) which is manufactured generally to the mil-spec, and that is not just wall-thickness, but rim thickmess as well.
The mil-spec for rim thickness is 0.064" max, 0.058" min, however SAAMI specify 0.064 and 0.054" min.

Much of the US 303 appears to be manufactured to SAAMI standards and towards the 'bottom end' of the dimensions - in fact some of it would be rejected if the mil-specs were applied.

The difference between the two (in the picture) would increase the 'effective headspace' by about 5 thou.
I wonder how many thousands of tons of brass are saved by manufacturing to minimum tolerance - built to a price !

A photo of Winchester 303 compared to PPU



Photo from Ed Horton