By and large, most military mausers were "controlled round feed" - and unless the leading edge of the extractor has been ground, then the thing MUST feed from magazine - was not designed, originally, to accept a single round dropped into the chamber. There is/was a "Score Hi" follower for Mauser 98 - sets the cartridge below the bolt centre line - below the extractor - then the case rim can slide up behind the extractor as the round is pushed forward into the chamber. As I recall, that Score Hi follower uses a "centre feed" concept - and therefore does not use the "feed lips" on the receiver. If your extractor nose has been ground, and if the person that did that left the length the same - will be "weaker" (less material) than an original NOS one - but will work to "snap over" a chambered round, and still engage the rim enough to pull the fired case back out. Some actions using that "single feed" idea had extra room cut out of right side race-way to allow that extractor to move to right to get over the rim - some Mausers do not have enough space for that - meaning single feed "made to work" by shortening the claw, besides grinding slope on leading face of it - which resulted in less engagement on the case rim.
I have a Mauser 98 here with a heavy barrel 243 Win barrel - would think that should be easy fix - Isreali's made bazillion 7.62 NATO from 8x57 Mauser 98 - they installed a block at front of their magazine box to accommodate that shorter round, but from examples that I played with, was no other mods that I noticed - same follower, other wise same mag spring, same box, etc. Would think same would happen using 243 Win, since case body is same as 308 Win - but not working - I can only get it to work, at all, by inserting a Score Hi single shot follower - that seems to work - but I can not get it to do same thing directly from magazine load - I suspect is something about the feed lips that are ground into the underside of the receiver, plus the timing when the 243 Win shoulder hits that feed ramp - which will be different than 308 Win - I think ...
An ongoing current project - I have a Parker Hale 1200 TX - made in 1969, I think. It is based on Mauser 98 and is a repeater in 7.62 NATO. Shown as such in Parker Hale 1970 catalogue. By 1976, that PH catalogue shows the Parker Hale 1200 TX Mk.III - now a single shot - no magazine at all - very different "guts" and "bedding" underneath that receiver - at least from the diagram. I am still trying to find a PH catalogue between 1970 and 1976 to find when they made that change - 1976 says it was "Mark III" - that would imply there was a "Mark II" and a "Mark I" previous to that, if PH was using the British military words - or might all be a marketer's B.S.
When you are looking to find a trigger, you might want to also consider the "cocking piece" that goes onto the firing pin - the trigger sear engages on the cocking piece - not directly onto the firing pin. Original "cheapest" military trigger and sear units used a cocking piece with "V" shapes on bottom - later Parker Hale and other commercial replacement triggers often want a "flat bottomed" cocking piece - is some examples on hand that someone attempted to weld the "V's" to be full, and then ground that cocking piece to be flat - I do not know enough about hardening metal, but I suspect such a welding job would require re-heat treating that cocking piece to make the leading face of it to be diamond hard - to resist wear of the sear dragging down along it.
There is a mauser "Shop Manual" by Jerry Kuhnhausen - a very good reference book, with a lot of "esoteria" about Mausers - no doubt is many other useful books - Ludwig Olson's "Mauser Bolt Rifles", for example - even 1950's books by Roy Dunlap has some neat tips - from the days when Mauser 98 milsurp conversions seemed to be the thing to do to get a "hunting" rifle.
Even the safety can take some thought - is several "modern" triggers that will have a slide safety that "blocks" the trigger from releasing - that will require some inletting into the stock to fit one in there - only the trigger sear is holding the cocking piece back. Original Mausers usually had an "over the top" safety lever - so usually straight to right was "on safe" and bolt was locked shut; then straight up was "on safe" but bolt able to be operated, then fully straight over to left and that was "fire" position. At least one country ordered their Mausers with safety the other way around - fully to the right to fire. Then companies like Timney and Dayton Triaster made "up down" two position scope friendly replacements that worked along the right side of the scope eye-piece. Parker Hale and FN had similar, but on left side of the scope. Parker Hale also made a slide safety/adjustable trigger unit that included an arm that came up through a slot in the receiver to "lock" the bolt shut, when that safety was engaged. I have installed one Gentry and one Dakota three position, horizontal swing safeties on a couple of Mausers here - they are three position - look and function similar to the safety on a Model 70 Winchester. All the safeties on the bolt, have about nothing to do with the trigger - on one that I installed, I replaced the "adjustable" trigger with a cheap, simple military one.
