Couple of quick observations, stick to the std. Mauser 98 actions--the 1936 Mexican is an oddball small ring barrel receiver and uses a unique bolt. If you wanted to change cartridges, it would be an expensive fix requiring a gunsmith.
The last rifle, the Spanish 93/1916 model, is an example of making a sporter out of a rare animal and actually decreasing value. This rare firearm came from the efforts of the Catalan separatists in Cataluna that were part of the Republican effort to produce arms. These were only made for three years and most of the receivers with this information were scrubbed. A lot of reports call these substandard in production quality as well.
Now for the longer part,
The last rifle's example is why milsurp collectors react so harshly to those sporterizing military rifles--the various markings, finishing, cartouches, stocks, hardware, etc. tell a story that is maimed and obliterated by the sporter process. On a rare rifle such as the last one, it is a financial loss, the firearm may be unsafe for firing live ammo safely, and history was destroyed--all to make a substandard sporter.
https://forums.gunboards.com/showth...h-Republican-M1916-Second-Pattern-Short-Rifle
If you want a good guide to Mauser actions in general with some information on sportering them--get Kuhnhausen's Shop Manual on the Mauser Action. There are better books on the actual sportering of Mausers but none are as good as Kuhnhausen on evaluating up to century old actions and parts.
Now, the k98. Parts, including new bolts, are still available. Most gunsmiths know how to work on them and determine whether or not a particular rifle is unsafe--a typical issue is lug setback as Mauser receivers are a case hardened sandwich over a softer core. Over pressure rounds or continuous use of a higher pressure cartridge than the heat treatment was designed for can produce lug setback and headspacing problems. Requalifying the barrel (setting it back) only delays the inevitable for a short time. Obviously, since so many Mausers were made, and rebarrelling is easier to do than competing designs, you will find these and barrels available in a variety of quality, finish, etc. The preceding models before the 98 Mauser should be used with cartridges and handloads that fit the pressure profiles of the original cartridge for the rifle. Metallurgy was not as well understood and production (heat treatment for example and the effect of impurities in the steel) of these rifles during the early smokeless era means that you really should not expect to use a modern 60000 psi cartridge in a receiver designed for 40000 psi.
The mauser 98 actions can be divided into country and when produced. If you want a sporter capable of modern cartridge pressures, then look for those made in the 1930's from Germany or the Czech Republic, post war from FN are fine (JC Higgins, Sears Store brand, used FN receivers for some of their sporting rifles), and some of the outstanding sporters from the Mauser mothership plant (Mauser banner label) at Oberndorf. German and Czech receivers made during WWII got progressively worse, there were supply problems with the steel, and some German ones were produced in factory prisons by slave laborers. I would personally avoid any made after 1943 to the end of the war in 1945.
Post war Spanish receivers are decent and several importers used Yugoslavian made receivers (Charles Daly for example) that are of good quality steel and finish. Steyr and later FN sold a lot of rifles to Latin America pre WWII and these are commonly encountered as well. Make sure that you get to observe the receiver below the stock line as some of these have horrendous pitting below it making the rifles unsafe to fire. A lot of unscrupulous or ignorant folks simply ground off material until the pitting disappeared on these above the stock line. There is also a need to remember that Mauser magazine lips are built into the receiver for feeding the original cartridge--alterations of these can affect feeding and can actually be dangerous when people wanting to feed longer cartridges grind and remove material from the receiver to allow it to fit.
My long winded post is simply to remind folks wanting to do this is to do your research before purchasing something that may not be suitable for what you want. I would also discourage folks from chopping up existing complete military surplus rifles as they will lose value in doing so and might be like the fellow who "improved" the rare 1916 model at auction listed above who destroyed a relatively rare rifle to make a potentially unsafe run of the mill sporter. A easy way to start is buy an action without a barrel to start--those which have the markings obliterated or already altered can often work. New barrels are available for Mausers, not so much for other makes which will require machining to work from a barrel blank or buying a used barrel of uncertain quality. For that reason, I would advise using a Mauser 98 action as a starting point giving the most options to sporterize.
Military surplus rifles were designed to be rugged, work in all weather, feed all sorts of ammunition, allow a bayonet mounting, and be accurate enough for minute of man. They were not designed to be sub MOA rifles--the designs themselves may be capable but to get there from an issued rifle is expensive and/or time consuming effort. If money is at issue, a Savage Axis will probably have a better trigger, fire new high pressure cartridges with aplomb, already be prepared for scoping, and be more accurate than most accurized military surplus sporters. If you want to take that journey, there are several folks on this forum who can help--LoonWulf, MachIV Shooter, Varminterror, GunnyUSMC, and also THR moderators as well.
By all appearances rifle #1 and #2 show some quality work. Rifle #3 the Spanish Mauser will never be in the class as the first two. It would cost serious money to duplicate #1 and #2. I suspect it would easily run into the thousands of $. Right, on standard calibers. What ever you do make sure you use good quality action and barrel-no junk.
in the form of a sporterized U.S. surplus 1903. I found this one still in .30-06 and it shoots too well to even unscrew the barrel for a polish & blue.... yet. No problem hunting with it but about 20 hours would tune it to a fine *legacy-grade* rifle.
