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The max COL of the .416 Rigby is 3.72". This makes the standard Mauser 98 action unsuitable or less than ideal to build a rifle in this caliber. Rigby built several .416 Rigbys on this action in the 50's and many had problems with bolt lug setback (even if Harry Selby's seemed to have been immune to this). Here is my solution.
The COL of US .416 Rigby cartridges varies from 3.55" for the Hornady 400gr to 3.625 for Federal 400gr loads. Both fit the magazine of my Browning FN .375H&H. Keep in mind that the Rigby develops a more than adequate 2400fps with only 47000psi of chamber pressure,considerably less than the 60000 psi of a .300 Win Mag. So if one were to limit themselves to a COL of .3625 a standard Mauser could work.
My FN has about .06" removed from the rear of the magazine the rest,.185" is achieved by lengthening the front at the expense of the bottom lug support,a less than ideal solution.
Option 1: Removing .25" from the rear, (.125 from magazine wall thickness and the same from rear wall of receiver)and modifying bolt stop to go .13" further back. This would allow factory US ammo to fit with little or no removal of metal from the front of a standard (.30-06 length mag). If you handload the cannelures of 400gr US bullets allow for this shorter COL.
Option 2: The neck of the Rigby is .5". The neck of the Ruger is.305". If the neck of the Rigby were shortened by .15", to .35" the COL would be reduced to 3.4" with Hornadys to 3.475" with other brands. A magazine length of 3,5" can easily be achieved by shaving .09" from the rear wall and .03" from the front.
I would refer to this shortened neck cartridge as a semi-wildcat because a standard Rigby chamber (no special reamers)and standard Rigby reloading dies would be used. There would be a slight freebore effect, about half of that when firing a .458 Win Mag in a Lott chamber.(Lowering pressure and increasing velocity).
Even with the bullets deeper in the case the huge volume of the Rigby would allow to exceed factory performance with much lower pressures than the Ruger. Furthermore cases would need nothing more than neck trimming and full length factory loads could be loaded in the chamber.

This technique could also be applied to the .404 Jeffrey with its long neck. In this case a .15" reduction in neck length would result in a COL of 3.35" which would require no magazine lengthening.

Edited by Wanabebwana (15/02/14 09:40 AM)