Jay, It is no secret that I have a fancy for uncommon firearms and historic firearms. Well, here is a twofer, and I suspect your readers may get a real "kick" out of this one!
First off, it is a M18A1 recoilless rifle, 57mm, made in 1945 by Firestone Tire & Rubber. There was a strong desire for man-portable anti-tank artillery in WW2, and the M18 was America's first recoilless rifle to see volume production.
At 45 pounds, it is a bit awkward for carrying – and even worse when carrying ammunition at another 5 pounds per round. But for comparison, the wheeled 57mm M1 conventional cannon in use at the time weighed several tons, so a 45lb gun did have some benefit.
The big weight savings in the M18 rifle came from using a recoilless system. In a conventional gun, the projectile goes forward and the gun recoils back. As projectiles get large and heavy, the gun recoils back with more and more energy. The recoilless action is unique in that it vents most of the burning powder out the rear of the rifle. Think of it as an instantaneous jet of flame pushing the rifle forward – just enough to offset the recoil of the projectile leaving the barrel. The end result is a shoulder-fired gun sending a 2.5lb shell a mile away. The side effect is an incredibly large and loud blast when firing - with most of that blast going up to 100 feet behind the shooter.
Everything about this gun is unconventional, including the ammunition. The cases are about 12" long and are intentionally full of holes. A paper or plastic liner is inserted into the case and filled with about one pound of smokeless powder. Projectile flavors include solid training rounds, smoke, high explosive, high explosive anti-tank, and canister rounds – which are essentially very large shotshells.
When a cartridge is loaded in the breech, the case walls are completely unsupported. The burning powder burns through the case liner and fills the breech with expanding gas. Some of that gas sends the projectile down the barrel, and most of that gas vents through the rear of the breech, through two kidney-shaped calibrated orifices. In the photo below, you can see the perforated case loaded in the breech through one of the orifices.
And as I said, everything about this rifle is unconventional. If you notice in the pictures, the projectiles all have rifling engraved on them. That is a feature designed to reduce the force needed to send a projectile down the barrel. When a round is loaded in the chamber, it must be rotated by hand to engage the rifling before the round seats fully.. This way, when firing, there is no energy lost to form rifling on the projectile – and less force on the barrel, allowing for the use of a lighter barrel.
The rifle is of amazingly light construction when you consider the scale of the charge and projectiles. The image below is the muzzle end, with a 30-06 round for scale.
The 57mm saw use in late WWII, throughout Korea, and limited use in Vietnam. This particular example has some fuzzy history. 1945 production, so I'm not sure if it saw use in WWII, but if it did it likely was in the Pacific, not Europe. Undoubtedly it served in Korea. It was eventually surplused out to Italy where it was used for many more years. After Italy retired and deactivated this gun, it made its way back to the US, and through a few hands before it ended up in my collection.
I was lucky enough to get the proper Italian subcaliber training kit (a recycled 6.5mm Carcano built into a 57mm shell!) , a depot-made .22LR subcal, and also a US 30-06 subcaliber kit based on a M1919 barrel. The previous owner was quite the collector and passed along canvas sets, ammo carrying gear, cleaning rods, scope illuminators, original ammo storage tubes – just about every accessory offered for the 57mm.
No gun in my armory would be complete without reloading supplies either – so an extra crate of projectiles and a bunch of empty casings should keep this running for a good long time.
And if anyone has a line of 57mm recoilless parts, please let me know!
Thanks for sharing that with us, Wally. I've shot the recoilless with the .30-06 insert, and it is truly something to behold. It's about the only time you will ever hear someone talk about a .30-06 being "puny" or the recoil of it being "mild"... This rifle is truly a fascinating piece of our military history, and I am thrilled and honored to both have been able to shoot it and to facilitate Wally telling her story.
Bring enough gun indeed.
That is all.