The main idea behind this cartridge is maximizing powder space of a standard case while keeping shoulder angle and neck length on the moderate side( s. Thoughts about Improving).

The 7x57Mauser is a typical candidate for improving due to its long neck, long shoulder and old fashioned body taper.

After fireforming you will have a cartridge which has about 9% more powder space than its parent case. 7mmMauserMaximum loads (after fireforming!) should be based on reduced 7x57AckleyImp. Data for working up. It is always a good idea to be cautious while approaching maximum pressure.

Its actual performance depends on several factors. As performance is most of all a function of powder space it is slightly more powerfull than the 7x57AckleyImp. And comes close to the 280Rem /7mmExpr..

The famous gunwriter Jon R. Sundra did basically the same modifications to the 280Remington case creating his 7mmJRS -many years ago:

 Comparing both cases strictly by their geometry -identical weight- results in a volume increase of 5.5 grs. of water.