by No1Mk3 » 06 Aug 2020, 2:33 pm
G'day LlovemyLE,
What do you mean "reliable dimensions"? There were no CIP/SAAMI specs for these wildcats and it was whatever your gunsmith made it. The original 303-270 was invented by J.Black Snr and was simply a 303 Mk VII necked down to take the .277 bullet. same original Cordite charge as well. The Super Cartridge 303-270 is also a necked down 303, 13.2mm rim, 11.75mm base, but were trimmed to 56mm case length after re-sizing. Cheers.
PS: Best way to make cases, buy the Simplex die set.