Let's begin with the introduction of the J. P. Sauer and Sohn company, the oldest still-operating firearm manufacturer in Germany. Their headquarters are in Isny im Allgäu, a town in the southern part of Germany. They manufacture a wide array of repeating rifles – model 100, model 101, model 202, model 404, and model 303, a semi-automatic rifle. In their offer, one can also find several shotguns, as well as slings, caps, cases, knives, etc.
Sauer 404 is the most expensive of all the rifles listed above. The buyer can choose from versions made of different material – wood, synthetics, and carbon. Its pros are the ability to quickly change a barrel (16 available calibers), a reliable manual cocking system, adjustable trigger pull weight, a cold-hammer forged barrel that guarantees a precision of less than 1 MOA, and a SUM Universal mounting surface.
Group hunts, especially of the driven type, are steadily gaining in popularity. A semi-automatic rifle is an excellent choice for such type of hunts because of the self-loading system and weaker recoil which is the result of gas-operated reloading. The semi-automatic Sauer 303 rifle is available in several versions – some are made of wood while others are made of polymer. The Artemis model has a shorter buttstock with a sleek pistol grip, making it suitable for women. Sauer 303 rifles feature a reliable manual cocking system, a direct trigger with a 950 g pull weight, and a cold-hammer forged barrel with a chrome-plated interior which grants protection against corrosion and enhances the barrel’s lifetime. From 2019 onwards it features the SUM mounting surface which had only been on Sauer 404 models before.
Until 2019, Sauer 303 rifles had an ISI rail on the action for mounting purposes. This unique mounting system is among the lowest mounting surfaces on the market. The notches for the recoil stop are identical to the ones found on a Picatinny rail. These notches ensure that the mount is fixed tightly, contributing to the accuracy and reliability of the shot. The mount is simple install and remove. On top of that, it is 100% repeatable. The ISI rail can also be found on a few Sauer 202 models. The mounts for this mounting standard are made by Sauer, Contessa, Dentler, EAW, ERA-TAC, Henneberger, INNOmount, MAK, Recknagel, and Rusan. Each manufacturer offers several versions of this mount, depending on the type of the optical device and the purpose of use.
As mentioned above, Sauer chose to unify the mounting standard on Sauer 303 and 404 rifles – Since 2019, all these are offered with a SUM Universal Mount. SUM is an elegant, technologically perfected, low-profile mounting surface. The low-profile design allows the shooter to quickly focus on the target without having to lift the head. It is robust, reliable, and guarantees a 100% repeatability. It is built into the rifle’s action, which adds to the durability. These rifles can compete with sniper rifles with a built-in Picatinny rail in terms of reliability and accuracy. Many different versions of these mounts are available, including the ones for various types of rail mounts (LM rail, Zeiss ZM/VM, Swarovski SR, Schmidt & Bender Convex) and ring diameters from 1 inch to 40 mm. SUM mounts are made by Sauer, MAK, INNOmount, Henneberger, and some others.
The change of the mounting surface on Sauer 303 models will surely cause confusion among customers & sellers at first – we must admit that the transition is somewhat controversial as there are now Sauer 303 rifles with both ISI rail and SUM mounting surface on the market. Nevertheless, there is a positive side to it as the SUM mount is among the most reliable and technologically advanced mounting surfaces available. ISI rail has a minor problem which must be pointed out. The mount is fixed onto the rail with a lever which often rubs against the aluminium action, leaving marks. This is more of an aesthetical problem as it does not affect the functionality and accuracy of the rifle, but still.