Umarex Thompson M1A1 Part 3

Umarex Thompson M1A1 Part 3

Built to perform

By Dennis Adler

The idea behind the M1A1 was to take the then current M1928A1 and modify the design to make it faster and less expensive to manufacture, in order to meet the needs of the U.S. Army, U.S. Army Air Forces (consisting of both Army and Marine Corps pilots), United States Marine Corp, U.S. Navy, and Coast Guard during WWII. The Thompson M1A1 design was adopted in April 1942, so this latest Umarex Legends model is based on a design that is now 78 years old. Compared to the rest of the Umarex Legends, the M1A1 is a youngster, historically. As the most refined (as in easiest to manufacture) of Brigadier General John T. Thompson’s designs, (Thompson passed away at age 79 in 1940, more than a year before the U.S. was drawn into WWII), the various Thompson designs leading up to the M1A1 had all been proven in combat (M1928A1), both by the military and federal agents (FBI and Treasury) during the Prohibition Era, U.S. Postal Inspectors, various state and local law enforcement agencies, and in foreign conflicts. The Savage Arms improvements to the M1A1 made the Thompson more efficient for combat use by simplifying the firing system, and building improved stick magazines that held 30 rounds, that were easy to load, attach and most importantly, remove to clear the action in the event of a jam. (The same design had already been developed for the 20 round stick magazines).

M1A1 and CO2 magazine comparison   

The simple combination of the CO2 within the BB magazine (first used with the Legends series in the M1932 Broomhandle Mauser Model 712 with a single CO2 cartridge) was expanded upon with the MP40 using two CO2 cartridges to power the gun. The design for the M1A1 is taken directly (internally) from the Umarex Legends MP40 submachine gun. The exterior design follows the look of the M1A1’s 30-round box magazine, which was approved as standard in December 1941 to replace the earlier 20-round XX and L-type drum magazines (which could not be used with the M1A1 design). The 20-round and 30-round magazines were lighter and easier to carry in quantity in the field.

If you look at the left side of an M1A1 magazine and the CO2 magazine, the profile is almost identical with the six witness holes and magazine guide channel. The BBs loaded into a forward chamber loading port and the magazine has a fairly easy to manage follower and spring. This is only seen from the front or ¾ views of the CO2 magazine, and holds the correct number of rounds for an M1A1.

Loading CO2 and BBs

This is the same as loading the MP40 magazines, with two 12 gr. CO2 cartridges loaded back to back in the CO2 chamber. With the seating cap turned down, both are pierced (one by a pin at the top of the magazine, the other by a pin in the seating cap) and the chamber fills with CO2. Loading BBs is a simple process, especially with a speed loader. Hold the follower and spring down below the loading port, pour in up to 30 BBs, carefully release the follower and you are ready to insert the magazine into the receiver. Pull the charging handle and the gun is ready to fire. (Be sure to keep the safety selector on SAFE when inserting the magazine).

Velocity checks

For today’s test I am using Umarex Precision steel BBs and firing 10 rounds on semi-auto through the ProChrono chronograph. The gun is rated at 435 fps. My first run with fresh CO2 clocked 438 fps, 431 fps, 430 fps, 430 fps, 431 fps, 431 fps, 432 fps, 433 fps, 431 fps, 430 fps for an average velocity of 431 fps and a standard deviation of 2 fps for 10 shots fired at 15 second intervals.

More impressive was my 21 foot target shot through the chronograph with all 10 shots (fired single action from the shoulder) inside the 10 and bullseye at 1.25 inches center to center with seven out of 10 in overlapping groups of no more than 0.25 inches. POA correction at 21 feet was 1-inch up and 1-inch right of the bullseye.

This is an impressive beginning for the shooting tests with the Thompson M1A1. Right out of the box (well, this is a sample gun and there was no box) this is one of the best handling and most authentic WWII era copies I have seen thus far from Umarex or any other manufacturer in terms of attention to detail, operation, and first test accuracy. I have handled several original Thompson models over the years, including one that was issued to the FBI in the 1930s, and though I have never had the opportunity to fire one, this gun feels right from past experiences. And there is another plus to the authenticity of the design, with all of the correct dimensions, the CO2 model will work with a number of actual WWII era M1A1 accessories that we will look at in the coming weeks.

In Part 4 we will have additional velocity tests with different BBs and more semi-auto tests for accuracy at 21 feet and beyond.