The Iconic American WW2 Thompson: the M1A1

This Thompson is being sold by Morphys on October 30, 2018. Note that I refer to the M1A1 in this video as a transferrable gun; it is actually a pre-May dealer sample. Sorry!

While the US Army was satisfied with the Thompson as a fighting weapon in World War Two, it was most certainly not happy with the gun’s exorbitant price tag. The Thompson was a very expensive gun, and the Army wanted to see that change. In March of 1942, engineers at the Savage factory submitted a simplified version for Army consideration, and it was accepted and adopted the very next month. Savage would transition from M1928A1 production to the new M1 pattern in June and July of 1942.

This new M1 Thompson had eliminated at last the unique and unnecessary Blish lock system in favor of a simple blowback action delayed only by bolt mass. In addition to greatly simplifying the production of bolt components, this also allowed the receiver internal shape to be much simplified. A further simplification would follow shortly, as the hammer and floating firing pin were replaced by a fixed firing pin milled into the bolt face in October of 1942 – this new type being designated the M1A1. Another 715,000 M1 and M1A1 Thompsons would be produced by Savage and Auto-Ordnance by February of 1944, when the Thompson was finally replaced by the yet cheaper M3 “Grease Gun”.

This is the fourth in a 5-part series on the development of the Thompson…


  1. “new M1 Thompson had eliminated at last the unique and unnecessary Blish lock system in favor of a simple blowback action delayed only by bolt mass. In addition to greatly simplifying the production of bolt components, this also allowed the receiver internal shape to be much simplified.”
    Finally! Which lead to natural question why this move was not made earlier? After all it should be in interest of Auto-Ordnance to make it cheaper, especially given fact that it did not degraded performance in significant degree.

    • Yet, as per Ian’s information the Blish has influence to RoF. Thus, it was not truly a “lock” in conventional sense of the word, but rather a ‘retarder’. Still, a desirable device.

      • Now I am confused. What was Rate-of-Fire for each version? Modern firearms query gives ~700 rpm for both M1928 and M1 versions, English wikipedia query gives 800 rpm for M1921, 600 rpm for M1928, and 600-700 rpm for what it call United States Submachine Gun, Cal. .45, M1 and 700-800 rpm for M1A1. D.50-1 Kennblätter fremden Geräts. Heft 1. Handwaffen. states that Maschinenpistole 760(e) which is Thompson used by British forces has cyclic Rate-of-Fire 500 rpm.

        Authors of Strelkovove orugie from 1947 (Soviet book describing most important foreign fire-arms) apparently failed in differentiating Thompson variants, and they describe “Thompson Sub-machine A-1 model 1928” with noticing that there exist “model 1921” which features front grip for left hand and lacking muzzle brake-compensator.

        General view drawing [of “A-1 model 1928”] shows sub-machine gun without front grip, with muzzle brake-compensator, bolt handle sticking upwards and drum magazine described as drum magazine (for 100 cartridges), it is described as delayed-blowback and there is mention of element made from bronze, mass without magazine is given as 4,54 kg and Rate-of-Fire as 600 rpm. But I am unable to say to which variant these data actually are belonging.

        Yet this pdf:
        at page 9 of pdf, states that the most effective fire rate, as determined experimentally and released as the “Model 1921-A” is the present standard of about 879 rounds per minute. All guns now released fire at this rate, with exception of the carbine and Navy version

        Interestingly it also mentions about planned other cartridge options (page 10) at page, namely .22 LR, .32 Auto, .38 ACP. Prototype of .22 was build, which mass was 3 pounds and overall length 16 inches. .32 and .38 never gets prototypes, but there existed 9 m/m prototype, which was able to fire both “9 m/m Mauser” (9×25 Mauser Export?) and “9 m/m Luger” (9×19 Parabellum), which was meant for demonstration for Belgians.

        at page 14 method of accomplishing slower Rate-of-Fire for “Navy version” is described as follows:
        The slowing down of the Navy action is accomplished by usinga lighter recoil spring, a more slender buffer of one-piece construction rather than two, fitted with a single fiber washer to absorb the shock, and a weighted actuator. Also, the firing pin spring is shorter.

        • After some search I find Ontwerp-voorschrift voor de Mitrailleurkarabijn van 11,43 mm. (1943) signed by J.F. van der Vijver, in language which I do not know completely, but judging from available values Vuursnelheid: 700 patronen per minuut means 700 rpm. Drawings shows 1928 version, so I presume it apply to it.
          Anyway I think we might terminally solve any doubts Rate-of-Fire, if we found Small Arms Training, Volume I, Pamphlet No. 21, The Thompson Machine Carbine from 1942.

          • It is Dutch,we bought some 1928 models just before Japan joint the second word war.
            Holland was already occupied by Germany and the Dutch Colonial Army (KNIiL ) was buying all they can get.My grandfather who was an officer carried a Thompson and a Vickers made P08 parabellum pistol when figthing the Japanese army at the battle of Java.Later in the war Dutch came into he service
            with Britisch Commando forces in England.They also used the Thompson.

          • I found Small Arms Training, Volume I, Pamphlet No. 21, The Thompson Machine Carbine from 1942, sadly it does not give Rate-of-Fire, as it states
            The sole object of weapon training is to teach all ranks the most efficient way of handling their weapons weapons in order to kill enemy. Instruction will always bear this fact in mind and will continually impress it upon those whom they instruct.

          • Interestingly, it states that effective range was only 100 YDS:
            The machine carbine is a short range weapon introduced for the purpose of engaging the enemy at ranges of from 10 to 100 yds. At greater distances the speed of the bullet is so reduced that it has lost much of its penetrative power.

          • Range of Thompson:

            That is a pretty incorrect and funny way to put it. For starters, I am sure a significant portion of SMG use was at ranges less than 10 yds (9 meters). For example when assaulting or defending a trench, 9 meters would be on the long side of firing distances.

            As for the maximum effective range, .45 ACP of course has no problems penetrating normal clothes (even thick winter ones) at ranges much longer than 100 yds. The main problems for long range shooting are the high arc trajectory, which makes hitting targets at unknown ranges difficult and long time of flight, which makes hitting moving targets more difficult than with faster projectiles. Both can of course be compensated by firing short bursts, but still the effective range of the Thompson or other .45 ACP SMGs is slightly lower than good 9mm Parabellum (especially with “hot” SMG loads), 9×25mm Mauser or 7.62×25mm Tokarev SMGs.

          • Interestingly Small Arms Training, Volume I, Pamphlet No. 22, Sten Machine Carbine also from 1942, contain identical text (The machine carbine is a short range…) with 10 and 100 yards values, so apparently it was copied from Thompson Pamphlet or from some another source.

    • Was not made earlier simply because Auto-Ordnance sales were nowhere near as great as John Taliaferro Thompson had intended or hoped. Lagging sales meant that the receivers with the Blish principal parts were sitting around gathering dust.

      The British “cash and carry” purchases in 1940 likely saved Auto Ordnance, particularly given the prices charged for each cased Model 1928 with two 50-rd. drums and five 20-rd. box magazines… My understanding is that the M1 and M1A1 did not appear in British use until 1942, by which time of course the Sten was flowing from the production lines.

  2. Regarding the decreased rate of fire of the M1A1: it could be that that the primer is actually set of slightly prior to the bolt coming to rest forward so that a slight effect of advance primer ignition is present.

  3. There are three possible reasons why the ROF slowed down when they adopted the fixed firing pin.
    1) Rebound. In the previous model, when the cartridge was fired, and started pushing rearward, the bolt already rebounded vs the receiver and was slightly retreating, so the recoil found less resistance.
    2) Advanced primer ignition. The fixed firing pin fired the primer when the cartridge was still seating, and so the bolt was still pushing forward due to inertia. So part of the recoil energy was used to stop the bolt.
    3) (residual) The hammer spring. It was compressed when the bolt was pushed forward, so it aided the rearward movement (the effect is not specular, since the hammer spring slows down the bolt during the forward movement only in the last mm of the stroke).

  4. Somewhere during my lifetime of unstructured reading, I saw a claim that somebody tried firing a Thompson without the Blish block in place, and it worked satisfactorily. Not sure how you’d do that other than by chambering a round and then releasing the bolt — preferably from behind a stout barrier, using a string to pull the trigger. You can read all kinds of crazy things if you try as hard as I have, so I await correction.

  5. This is a question for Richard from Holland. Was your grandfather able to get out of Java before the surrender?

    • Hello,no my grandfather was made prisoner of war.( it was in 1942 when Dutch East Indies surender).He was shipped to the Island Sumatra and forced to be railroad worker at the ” pakan baroe ” railroad.He survived and nearly dead he was found by the Britisch red cross with Lady Mountbatton.She personelly send him ( and a few other very ill suvivors) to a hospital in Singapore.
      In the spring of 1946 he returned to Java to his wife and children.Went back in service at KNiL and served in the Indonesian independent war against the freedom fighters.In 1950 the war was over and the Kolonial Army no longer needed.So the covernement shipped him and his family to Holland.He died a few years later.

  6. I have heard a lot over the years of what the troops thought of the Garand and the M1 Carbines, but what was their likes and dislikes, if anyone knows, regarding the Thompsons? Ian mentioned the Marines liked them when they first got their hands on them, but that was a number of years prior to WWII.

    • Soviets soldiers disliked this weapon, I searched (database of memoirs) and Thompson is mentioned rarely and any attitude is said only in 3 cases – few other contain mentions of this sub-machine gun, but limited only to information that author of memoirs was at some point using this weapon.
      Anyway, 3 opinions:

      D. F. Loza (you might know him as author of Commanding Red Army Sherman Tanks) described Thompson as crappy and note that they [tankers] prefer German SMG with folding stock [MP40]

      P. G. Kolosov, who was fighting in northern areas
      In 44 year we got “Thompsons”. We did not get accustomed – spread big, range rather small, cartridges heavy – you can not carry a lot of them. We were accustomed to domestic [PPSh]. Usually I carried one drum and 4 stick magazines

      I. G. Melnikov, AA defense officer
      Q: Your personal weapons?
      A: TT automatic pistol, Mosin carbines for soldiers, later we got Thompson from Lend-Lease. Very poor weapon in comparison to PPSh

      Additionally it looks that Soviet Union received shipment of .45 ammunition of dubious quality:

      • No surprise there. The Thompson just wasn’t cut out for the needs of the Russians. They preferred weapons with simple nature and good performance. Thompson guns were a bit complex (the early versions anyway) and required lots of work to keep serviceable. I could be wrong.

        • Nonetheless according to this pdf (page 27):

          At one time Soviet Union request from United States Machine Guns, Complete With Ammunition, .38 Cal. and Thompson Sub-Machine Guns .45 Cal.
          in quantity:
          120000 – .38 cal
          127878 – .45 cal
          Soviet Union was informed that No .38 cal. in production
          I am wondering what they actually means under “.38 cal.” (.38 Auto? .38 Super? .380 Auto? Yet another cartridge)? and did they were asking for “.45 Thompson” and “.38 Thompson” or maybe another .38 sub-machine gun, which name is not given.

          • .38 ACP and .38 Super have the same cartridge dimensions and would probably function adequately in the same straight blowback SMG, assuming that the bolt is heavy enough to handle .38 Super without the gun beating itself to death. Perhaps the Soviets thought that either one would be acceptable and they just didn’t want to limit options too much by being too spesific? In any case, .38 Super is practically the same as early production .38 ACP was before the loads were reduced so that the Colt M1900 could withstand them better.

        • After viewing Ian’s shooting video today, I would say that the main complaint the Soviets had about the M1A1 (which was the model they mostly received) was probably poor controllability. P.G. Kolosov’s opinion below also supports that theory. The RoF of the M1A1 seems to hit the zone where the gun jumps around a lot instead of being a more steady push, and of course .45 ACP has a significantly higher recoil impulse than 7.62×25mm to begin with.

  7. The British Army bought a huge number of M1928> from late 1939, the Small Arms School Corps Museum has on its website a article on the acquisition of the weapon. It telling of the huge number (some 270K) lost in the sinking of ships in the North Atlantic in 1940-41.

  8. My grandfather carried an M1 Thompson in Algeria, Tunisia, Sicily, Italy, France, and Germany, I have a great piece of artwork done by a war buddy of my grandfather with the gun drawn in it, so for that sentimental reason the M1 Thompson is the one NFA firearm that I would really love to own.

    I just wish I could still register weapons under the NFA so that I could buy a historically accurate reproduction and have it legally made select fire because I can’t afford the $20,000+ price for an original. Yet I can’t bring myself to buy one of those semi-auto only reproductions as to me it would be like buying an 1860 Springfield with a matchlock or a muzzle loading M1903 rifle.

    • In the EU we can own a Thompson as it is made non shootable (” demil” or “deko” ) by welding en drilling some parts.
      Al original but not able to shoot with..Cost of a M1A1 is about 400 euro.

  9. By the way, I have found it a few years ago:

    “When the war broke out, Sefried intended to become a pilot, until the Air Corps discovered he was color blind and made him a firearms instructor instead. A range accident with an M-l Thompson gave him cause to study the gun, and he devised a means to convert it to fire from a closed bolt. His invention was studied, and praised by various agencies, but was not adopted because the Thompson was due to be phased out in favor of the M-3 greasegun.” (PETTY, Charles E.: Harry E. Sefried II: Gun Designer Par Excellence – A Modern Day Browning… American Handgunner March/April 1983 [])

    Is there any knowledge about Sefried’s closed bolt M1 Thompson?

    • I would like to know the answer to that question as well.
      Perhaps it is ergonomics or that most soldiers are right handed? Most guns(I think) also have the charging handle on the right.

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