I have a chance to buy a commercial FN Mauser chambered in 458 Win. I've seen lots of standard length Mausers in 375 H&H. Would it be safe to open up this rifle to 458 Lott? Thanks!

fla3006--

It's only safe if you replace the magazine box that duplicates the old Orbendorf style that opens the action to the rear as well as front.

DON'T do the FN way!!

Thanks Mr. Belk. Did FN remove metal around the feed ramp to create a magnum length action? How about Interarms Mark X 375 magnums, do you know if they opened up their actions at the rear?

Fla3006---

Only the original commercial Orbendorf Mausers had the bottom metal that allowed them to open the M-98 correctly......... until Burgess and Blackburn did it for the custom gunmakers.



Here's an FN 375 H&H that bulged the bottom lug recess. I've seen more Mk-X actions ruined than FNs.
An extra .125 of steel prevents this and gives a much better angle to the loading ramp.

The action ALSO has to be milled (double taper with a radius) to the front to move the shoulder stop ahead for the cartrige you're going to chamber for. Otherwise the shoulders are crowded and the tip of the bullet crosses the boreline before it gets to the chamber.

Thanks again!