.303 British (left), .416 Strauss (middle, loaded with a 350 gr Speer bullet in a Norma case)

The parent cartridge is the .303 British. It is blown out to .416 caliber and loaded with a 300 grain Barns-X or 350 grain Speer bullet and S265 Pistol powder (a local South African powder). The 350 grain bullet is propelled at 2300 fps and generates 4112 ft/lbs of muzzle energy. The lighter bullet is pushed out at 2500 fps and generates 4164 ft/lbs of muzzle energy.

The performance seems similar to the .375 H&H Magnum. According to Cartridges of the World (11th Edition), the .375 H&H can push a 300 grain bullet at 2530 fps, generating 4265 ft/lbs. The small caliber .375 bullet would have greater penetration than a .416 bullet. The cartridge works about to be about 20% less powerful than a .416 Rigby

Piet uses the cartridge in a with with a P14 (Pattern 1914 Enfield) action. The groups are not all that great as he does not have a custom die set and has to use a .405 Winchester die for seating the bullet.

The .416 Strauss P14 (click to expand)

I think this is a very compelling cartridge. I am surprised I had not heard of .303’s necked up and turned into big game cartridges before. It seems like a good idea as I am sure Africa is has more than its share of .303 surplus rifles.

A big thank you to Piet for emailing me the photos and information.