World's Largest Machine Gun: Inside the 40mm Bofors Build

Ira, our friend and resident heavy weapons expert showed up with a pretty big surprise a while back, a 40mm Bofors anti aircraft automatic cannon. Needless to say, this is the most incredible gun to ever roll into the Red Jacket shop.

The Bofors is a fully automatic anti-aircraft cannon that was one of the most popular medium-weight anti-aircraft systems during World War II on both sides. It can be used from the ground or from a ship, and the cannon remains in service as of 2012, making it one of the longest-serving artillery pieces of all time.

Ira's Bofors already worked when it showed up at the door, so all we needed to do was get the road dust cleaned up and get it out to our own personal demonstration spot. This is simply the world's largest machine gun, shooting150-200 rounds per minute, weighing in at 4,370 pounds and costing its lucky owner about $150,000 in working condition.

Presentation is important with a gun like this one, any client willing to drop that kind of coin on this once-in-a-lifetime gun is going to have to be more than impressed. You want to put the gun in a setting that makes it real for him.

The gun has over 500 parts and came with a pretty thick manual written entirely in Finnish, which made it all the more nerve racking when Kris discovered the gun wasn't in working order about 96 hours before Ira's client was going to give it a damn test drive. We were getting pretty nervous until we discovered a small gear that had come out of place during transit that was preventing the barrel from articulating.

Seems it was a small and simple fix -- I just used a dowel rod to pop it back in place-- and we were on our way to one of the most incredible range days of my shooting life.

But wait, it couldn't have been that easy. The charging handle didn't work, and that's the only way to manually load the Bofors. Sometimes things just aren't simple.

Joe, Flem and Kris had to remove the loading tray and replace the pin a was missing from the feeding mechanism. Can anyone else see the irony in a tiny pin is preventing us from shooting a nearly 5000-pound cannon?

The cartridges for the Bofors weigh about five pounds each and pack enough charge to send a two pound projectile out of the barrel at roughly 2800 fps (the ejected cases move at about 200 fps coming out of the back of the cannon).


Firing it on full auto with a good loader is something that simply has to be felt to be understood. It's a full mind and body experience. The targets moving, you're moving the gun to keep it on target, the noise is overwhelming, the smoke from the muzzle blast is nearly blinding and the steady, rhythmic recoil seems to go through every part of your body. I only got to do it once but I promise you it's an experience I'll never forget.

In the end, Ira did good business and we had a great time working with him. See ya'll next week.

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