Home Forums Hunting & Shooting Mausers and Military Rifles Rifle, No. 4 Mk I, 300 WM conversion.

Fawkes, I'm curious. I know why you made the video, but I think you should have considered bolt thrust, not the pressure generated by the cartridge. Cartridge pressure acts upon the bolt face, which in turn, acts upon the lugs. There is an approximate 32% pressure increase on the bolt face, transferred to the lugs. This is from 303 to 300 WM.

303 British - approx 3900 kgf bolt thrust
308 Win - approx. 4660 kgf bolt thrust
300 WM - approx. 5700 kgf bolt thrust

MAP x Aext = kgf

The No 4 action was designed to shoot the 303 British, which generates 3900 kgf of bolt thrust. How long can the mechanism take the increased bolt thrust generated by the 300 WM before it fails? Rather than compare the bar (pressure) increase from 308 to 300 WM, you should be comparing the bolt thrust (kgf) of the 300 WM to the 303 British. The test is really about how much abuse the lugs can take, going from a relatively sedate 3900 kgf to 5700 kgf. After all, with the exception of the bolt face, the bolt is original issue.

I think we can all accept that increasing the pressure to 300 WM levels would eventually render the rifle unserviceable. How many shots will it take before the bolt distorts? You will need to repeat the test. Because of the design, I expect the bolt should twist, but not come apart catastrophically.

Have fun!