The first Stevens 520 appeared in Stevens' 1909 Catalog #52 and was also offered for sale in the Fall 1909 Sears & Roebuck catalog. It is easily recognizable by its "Humpback" double hump receiver. It had a round slide release knob on the left side of the receiver, a visible breech locking bolt on the top of the receiver, and base models had a rounded pistol grip on the butt stock. The fore grip was ringed and uniform in size. The trigger housing was retained with three screws and the safety was a lever located inside the trigger guard in front of the trigger. The cartridge stop was a rocker design with a set screw on front right side of the receiver. There were other models including a Model 522 trap gun and the 525, 530, and 535 with increasing levels of engraving and stock quality (some straight grip) and fore grips. Internally there was an inertial slide release block that was affixed to the inside of the receiver. This inertial release used the recoil of a discharged round to unlock the breech. The action was designed to only unlock after firing or with use of the slide release and not by dry firing like many modern shotguns. All model 520s were only offered in 12 gauge until 1928.
Around 1918, Stevens provided a 520 trench gun prototype to the US military for service in World War I. Supposedly several examples were made but no known examples survive. It had a unique two piece heat shield/bayonet lug.
When Savage Arms purchased Stevens in 1920, the Model 520 was updated incorporating several design changes that were emerging prior to 1916. These include a relocated slide release button, moved from the left side of the receiver to the left side of the trigger plate, and a redesigned inertial slide release, incorporated into the design of the trigger plate.
In 1925 the Model 520 first appeared as a store branded gun when it is sold as the Ranger Repeater Model 30 by Sears and the Western Field Model 30 by Montgomery Wards. Around this time the inertial slide release blocks are removed and replaced with a spring that provided forward pressure on the slide release. Guns made after this time could be unlocked after a dry fire with forward pressure on the slide.
In 1928 the first sub-gauge Model 520 was introduced when a 16 gauge option was offered. It was followed in 1930 by a 20 gauge Model 520.
The Model 520 last appeared in a Stevens sales publication in 1928 and 1929 (Catalog #57) but remained in full production until 1939. During this time it was sold as a store branded gun and under Stevens' budget line Riverside Arms. The shotgun went through several design changes during this period. Most notably was a redesign of the cartridge stop in 1933 and the relocation of the safety, from inside the trigger guard to behind the trigger in 1937.
Model 520 production ended in 1939 and it was replaced by the improved Model 520A in 1940.
The redesigned Model 520A was closely related to the Model 520, utilizing the same takedown action and locking breech block. The receiver lost the distinctive double hump and had a flat top and squared-off back end. The safety was moved to the receiver tang and the trigger housing was redesigned to use a coil mainspring instead of a flat bar mainspring. The 520A continued to be sold as a store branded gun and under Stevens' budget line Riverside Arms (stamped Model 520). The 520A was never shown in a Stevens sales publication, it only appeared in Sears & Roebuck and Montgomery Wards catalogs and in Stevens component parts catalogs (the only source where it was identified as a 520A).
Stevens halted civilian production in 1942 to make weapons for use by the US military during World War II (see Model 520-30 below). Civilian Model 520A production resumed after WWII, again as store branded guns, and continued until 1947.
The Model 620 was introduced in 1927 and is a streamlined version of the original 520. The safety was initially located inside the trigger housing just like the Model 520 but by 1929 it had been changed to a cross-bolt located behind the trigger. The stock was attached by a bolt connecting the receiver and trigger tangs through the grip of the stock. Initially the 620 was only offerd in 12 gauge but a 16 gauge followed in 1928 and a 20 gauge was introduced in 1930.
The Model 620A began production in 1940. The main difference between the 620 and the 620A was how the stock attaches. The 620A used a long draw blot through the end of the stock and did away with the receiver and trigger plate tangs used on the 620. Without the trigger tang, a flat main spring had no place to attach and the 620A had a shortened trigger housing using a coil main spring. Civilian production of the Model 620A halted during World War II but continued afterwards until 1955.
Model 520-30 and 620A (US Military)
During World War II, Stevens began producing both the Model 520A (renamed the Model 520-30) and the Model 620A (labeled as the Model 620) as trench guns, riot guns, and long-barreled training guns for the US military. Trench guns were produced with 20 inch barrels (cylinder bore) and had a heat shield with a unique pinkish anodized bayonet lug attached to the front of the barrel (late war examples had a small "S" stamped on the left side). The receivers of both models were stamped on the left side (from front to back) with a small "P" and ordnance bomb, "Model 520-30" or "Model 620", and a small "U.S." over the trigger. Model 520-30 trench gun barrels are marked "Proof Tested--12 Gauge --2 3/4 Inch Chamber--" on the left side and have another small "P" and ordnance bomb and the "J Stevens Arms Company" address on the right side of the barrel. This was done so that all the markings could be read with the heat shield installed. Some Model 620 trench gun barrels were marked in the same manner as the Model 520-30 trench guns and some had all the barrel markings on the left side. Trench guns were also fitted with a sling swivel in the stock. Riot guns also had 20 inch barrels (cylinder bore) and had all the same martial markings, except that all the barrel markings were on the left side. The long barreled training guns were marked in the same manner as riot guns and were mainly used for aerial gunnery training. Total wartime production of all Model 520-30 shotguns was 33,306 and all Model 620 shotguns was 12,174. After the war the US military standardized both the Model 520-30 and the Model 620 and kept them in the inventory. They were used in the Korean War and as late as the Vietnam War.