Thread: 303 MK7 load data?

Greetings @Old_School and all,
First thing, do not fire the MkVII ammo. The primers are both corrosive and wreck the cases with the first shot. Not that you are likely to reload it with its odd size Berdan primer. Barrels need to be cleaned with boiling water the day of shooting to prevent the damage. Additionally the cordite is very erosive, the reason many .303 rifles have severely eroded throats.
.303 data is all over the place. My rifle with a new two groove 25 inch barrel approaches the Hodgdon/ADI data but other more used rifles can fall 150 fps or more short. The Hodgdon/ADI data is for an earlier and slower version of the powder so max loads need to be cautiously approached.
But wait there is more. If cases are full length resized with the die down hard on the shell holder their life will be short with cracking showing just above the base as early as the third load.
If all this sounds like doom and gloom it is not meant to but the .303 is a cartridge with some unique challenges that need to be considered. Keeping pressures low and neck sizing will get over most of the problems. I started handloading with a .303 around 1970 and ran into problem after problem. After a while I spat the dummy, sold my .303 rifles and bought my first .308. Now 50 years later I am happily loading for 2 .303 rifles with no problems. Please ask questions if you wish.
Regards Grandpamac.