There are four basic sizes of Mauser actions. Two of these are rather uncommon and two of them are quite common. Mauser actions have been manufactured by a large number of companies in many different countries for over 100 years.
While the following guidelines are accurate, they are not to be taken as absolute. There are exceptions to every rule. The most common actions you will find are known as large ring and small ring actions. The term “ring” when it applies to a Mauser action refers to the area at the front of the receiver into which the barrel shank is threaded.
Mauser actions utilize two ring sizes. A small ring action has basically the same external profile from front to rear. The outside diameter of the action at the front ring will be 1.3" across. The large ring action has a slight step or swell at the front of the action and the ring will measure 1.410" across.
Typical, M98, Large Ring Mauser Action Pictured Above
The smallest factory Mauser actions are the Short, or “Kurz” actions, that were made by Mauser for the commercial market prior to WWII. Almost all of these were small ring actions, although at least one specimen of large ring Kurz exists. These are true 98 pattern actions that cock on opening. The bolts, receivers, firing pins, extractors and bottom metal are unique to that model and are not interchangeable with other Mauser actions. The overall length of the actions is about 8.125". These actions are among the most uncommon Mausers, quite rare and highly desirable to collectors.
The next size larger is the so-called “intermediate” size action of which there are several examples. The most common of these are the 1893-1895 Spanish Mausers and the 1894-1896 Swedish Mausers. These are the pre-98- style, small ring Mausers that have the long, non-rotating Mauser extractor, familiar ejector box on the left side (rear) of the receiver and the enclosed staggered-round magazine.
They lack the third (safety) locking lug at the rear of the bolt near the bolt handle root and they cock on closing. The bolt shroud at the rear of the bolt does not have the gas deflection flange of the M98 shroud. These actions have an overall length of about 8.5".
Slightly less common intermediate size actions are the 1910, 1924, 1936 Mexican, and the 1924 Yugoslavian. These are also about 8.5" long but have the features of the true 98 pattern action. They cock on opening, have the rear safety lug, and have the 98- style “flanged” shroud on the bolt. The 1910 and 1936 Mexican actions are small ring actions while the 1924 Mexican and Yugoslavian actions are large ring. Parts on all four of these actions are for the most part interchangeable; bolts, bottom metal, firing pins, etc.
The fourth size of Mauser action is the Magnum size action. These were built in limited numbers by Mauser and are slightly over nine inches in overall length. Magnum-sized, Mauser-type actions have also been built by other manufacturers like Brevex (France), BBK (Korea), and others. Each of these actions is unique to the manufacturer and parts are not interchangeable. These are not commonly encountered and original Mauser specimens are desirable to collectors.
The third size of actions is the “standard” size action. This action is approximately 8.750" long. It is a true 98 pattern, will cock on opening and has the third locking lug near the bolt handle. It also features the bolt shroud with an external gas flange that was designed to deflect escaping gas away from the shooter in the event of a blown case. This is the action most commonly encountered today on military 98 rifles, converted 98 sporters, and 98 pattern commercial rifles like the Interarms Mark X. They are found in both large and small ring configuration. Nearly all parts are interchangeable between these actions. This action was used as the basis for Mauser military 98's by dozens of countries and millions have been produced. They are still popular today for building sporting rifles.
This has been a short list of the different sizes of Mauser that you will encounter. If you are in doubt as to which type you own, get a good set of calipers and measure the front action ring then refer to the text. If you are looking for more information on the Mauser Rifle then get yourself a copy of the book, Mauser Bolt Rifles by Ludwig Olson. This outstanding book is the absolute best and most complete source for information on Mauser Rifles It’s available from Brownells.