Spitfire: The Semiauto That Became a Machine Gun

The Spitfire is a firearm with an interesting importance in legal history. Originally designed and marketed as an open-bolt semiautomatic-only carbine, it was determined to be a machine gun under the law in 1968, and all examples were required to be registered or destroyed. The reason was not its open bolt design, but rather because the safety lever could be used to hold the sear down and allow fully automatic fire without any alteration to the gun. This example was duly registered, and it now a transferrable machine gun.

Aside from this brouhaha, the Spitfire was simple a very poor man’s Thompson lookalike – although functionally it is much more like the M3 Grease Gun than the Thompson. It uses M3 magazines, and is cocked by simply pulling the bolt back with a finger, like the M3A1. The construction is extremely crude. Following its machine gun ruling, a series of very similar guns were produced by the same designer which used a closed bolt operating system to avoid the legal issues – the Volunteer carbine in particular.


  1. What is the finish on the lower receiver? spray-paint? That is the worst surface treatment I have ever seen.

  2. Ian,
    After viewing the Spitfire video I’m curious if you want to look at an M1 Thompson I have on a Form 4 with a Merle Bitikofer 22lr conversion unit and SRT can installed. It works well with Black Dog 30 rd box mags and a 50 rd drum and is “movie” quiet with sub-sonic ammo. Several attempts were made to make 22 lr conversions for the Thompson but most were unreliable. Merle’s work great.

  3. “(…)safety lever could be used to hold the sear down and allow fully automatic fire without any alteration to the gun(…)”
    So this weapon is full-automatic capable due to design error?

    Were stock used sourced from original Thompson stocks? If yes how they get stock of stocks? Were loose Thompson sub-machine gun available as parts back then?

    • Plenty of loose Thompson bits have been wandering around since the 2nd WW. It was a legal full auto & semi-auto available in the US before the 2nd WW.

  4. Open Bolt Guns that could be easily MODIFIED to fire full auto were the ones targeted. I remember ads for the Spitfire (I am that old).

  5. Almost any SMG with an open bolt “could be easily MODIFIED to fire full auto”.
    It is enough to turn off the disconnector one way or another.
    I remember that later ultrasound transformations appeared at the request of ATP when it turned out that the early modification was easily rolled back.
    In closed bolt systems, this also works in most cases.
    The worst such “modification” lends itself to systems with a hammer, which do not have safety from being fired when the barrel is not locked.

  6. Yeah, moral guardians strike again. “Oh no, he’s got a machine gun, and it’s so scary!!” They’re so dumb they couldn’t tell a bolt-action rifle from a javelin, mostly because they’re too busy hiding under the table, cowering and screaming bloody murder to even look at whatever is frightening them. No, I didn’t intend to rip anything from a comedic opera…

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