Squarebridge

Von Gruff built himself a 404 on a Columbian Mauser so hopefully he will come in on this thread and offer you a few pointers.

I have an original Oberndorf Mauser opened up to 404. When I got it from Africa it had only just been worked on and did not feed cartridges from the mag at all well. It required a good push on the bolt and cases were being badly scratched.
Before taking to the feed rails and guides I carefully studied the feeding process and could see that it was the extractor that was not allowing the case head to slip into place until late into the feed process, hence the cases were being forced along the rails before eventually popping up inline with the chamber. A small stoning to radius the bottom lip of the extractor was all it took to have my Mauser feeding like a hot knife through butter. The big 404s just pop up under the extractor and slip into the chamber. Even cast bullets feed no problem at all, especially Von Gruffs 350grainers which have a flat meplate and I understand do not feed quite so well in VG’s converted Mauser.

Now your feed rails will need modifying but don’t overlook the extractor as a cause of feed problems.

Good luck.