Firearm Showcase: Early 1900s Mason (and Browning?) Automatic Shotgun at the Cody Firearms Museum – HIGH RES PICS!

In January, just before the 2017 SHOT Show, I got the opportunity to travel to Cody Wyoming to visit the Cody Firearms Museum at the Buffalo Bill Center of the West, to see some of their rare firearms and bring photos of them to our readers. Over the past two weeks, we’ve been taking a look at some of the firearms from the Museum’s vault which are not on display, and today we have another very special firearm for your viewing pleasure.

Now, I admit, I don’t actually know what this gun is, exactly, but I have what I think is a very good and well-informed guess. I believe this to be a prototype semiautomatic shotgun developed by William Mason between 1900 and 1905, based on a system developed by John Browning before his termination at Winchester in 1903. Unlike the Mason semiautomatic rifle we looked at earlier, I do not actually have the patent for this shotgun, because it appears no patent was ever filed. However, we do have patents from Mason and Winchester for two other weapons, similar designs from 1900 and 1905 between which this shotgun appears to fit. One is a unique repeating shotgun, and the other is a gas operated semiautomatic shotgun (the patent for which appears to be the first for such a gun).

The actual gun itself is a bit of a mystery. It has a toggle action and appears to be intended as a semiautomatic, but the barrel is fixed, suggesting that this may have been a very early attempt at a delayed blowback action. Alternately, given the other patent, it’s possible this shotgun isn’t supposed to be semiautomatic at all, but rather a repeater, with the user intended to operate the toggle manually. Without having taken the gun apart, it’s very difficult to know exactly how the gun was intended to function.

We can see some resemblance in this shotgun to John Browning’s first semi-automatic shotgun prototype – a prototype which was probably actually made by Mason himself. Note the similar toggle-break action, and details in the screws and the contour of the triggerguard, all suggesting the same craftsman:

If you’re interested in seeing more of the Cody Firearms Museum, I highly recommend taking a trip out to Cody, Wyoming to see their awesome and extensive collection. They have over 7,000 firearms, about 4,000 of which are on display. In particular, if you have an interest in Winchester firearms and their history, Cody is the place to be. If just a visit isn’t enough for you, then check out the museum’s 79-page book, which highlights some of the finest pieces in their collection!

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • Major Tom

    It’s not related to the Auto 5 is it?

    • Anonymoose

      Maybe as an prototype alternative, since the Auto-5 came around about the same time and Mason worked with Browning for quite a while.

    • Distantly, sort of.

    • AK

      I would say only in concept, as in “self-loading”. Mechanically completely different action, as an Auto-5 has a long recoil system, which is similar to a modern pistol, except that the barrel travels the entire lenght of the action as well.

      A toggle action is a blowback design of sorts. The main problem I see with the use of any blowback system in shotguns is the diversity of loadings, which make the tuning of the parameters very difficult. Even the Auto-5 has a feature to adjust for trap vs full power loads due to this same difficulty. In a toggle design, it could perhaps still be done with some clever mechanics, like an adjustable pivot. A toggle action is not the most durable, why it hasn’t been popular for the past 100 years anymore.

  • Darren Hruska

    Hiram Maxim actually had patents for a toggle-action, semi-automatic shotgun as far back as 1886, prior to Browning and Mason.