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U.S. M-18A1 57mm Recoilless Rifle


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Remanufactured U.S. M-18A1 57mm Recoilless Rifle

Started out life as a demilled pile of scrap, restored to it's former glory; as a Sub-Caliber shooter. Currently set up to fire .308, but can also be setup with a .30-06 barrel; uses 1919 barrels. Here are some pictures of it mounted on 1917A1 tripod, but I also has a bi-pod. The optics are clear and it shoots accurately.

 

The work was done by Steve Carlesco, of Gunsmith Inc. (GSI) in Guilford, Connecticut. I would highly recommend Steve, he did a great job, was fast, professional, and a pleasure to work with.

 

Paul

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Great restoration job. Looks like you have one of the M18 to M18a1 conversions. I built a 50 BMG sub cal and made it recoilless with ports in lower part of M3 barrel used full length. It is welded so a 57 round will not chamber. It is a handfull and will shread a cardboard target if placed behind. The 57mm full bore is hard to imagine. Dad was in one of the first units to have these in WWII.

 

http://www.hunt101.com/data/500/recoilless_snapshot1.png

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I have a 57 also so redone. They did not port the bbl and the plate at the chamber is solid. Kicks so hard the M1917A1 tripod lifts up in the front and scoots a smidge. Can you tell me the info on making it recoiless ? Number of holes , are the angled or straight in , plates to direct the blast back , etc.

Because it's already assembled , I've been thinking of welding a plate in front of the .50 barrel inside the 57 tube ( with a big hole in the center ) to act as a blast catcher to cut down the recoil .

Thanks , Chris

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I have a 57 also so redone. They did not port the bbl and the plate at the chamber is solid. Kicks so hard the M1917A1 tripod lifts up in the front and scoots a smidge. Can you tell me the info on making it recoiless ? Number of holes , are the angled or straight in , plates to direct the blast back , etc.

Because it's already assembled , I've been thinking of welding a plate in front of the .50 barrel inside the 57 tube ( with a big hole in the center ) to act as a blast catcher to cut down the recoil .

Thanks , Chris

I ported it close to the chamber. You lose a lot of velocity. I had email from someone else who had experimented on ports. I used the data but angled the holes 45 degrees. Not sure if it really made much of a difference. The full length M3 barrel had to be drilled then EDMed due to stellite liner. EDM leaves the bore smooth. Fortunately have lots of machinist friends with tools. I have a baffle on adapter to block flow from ports in case pressure built up in chamber but have not tried to measure it. No need to do it. A larger hole further out with baffle might be just as good but only way to tell is make one. I can get some pics of it BUT not responsible for design. Even with the little 50BMG is is a monster. Many years ago MG news (or SAR) had an article on someone who converted to 50 without compensating. They said the same thing, lifted the tripop and could flip. I did enjoy reading about it as I did not had an M18 yet.

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I had thought of making mine into a 50BMG but elected against it based on the following:

 

- The amount of recoil in 50 BMG and the inherent weakness to the front and rear tripod attachment points. Glad I decided not too.

- The need to download, to not damage these attachment points.

- I can't image the weight of the 50cal M-2/3 barrel compared to the 30cal 1919 barrel. Would need a jeep to move the whole set-up.

 

But I must admit the night time back-blast is impressive.

 

Practical, heck no. Fun yes.

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You don't need a jeep but a pack mule or a kid is a good idea. The mules dont talk back or shoot up your expensive ammo. :lol: I prefer the M1917a1 tripod but they like shooting it off hand. I have considered cutting the barrel and fluting both barrel and adapter but that is a lot of work. The 50 is fun even with blanks. I made it so other calibers can be used but it will not chamber a standard military adapter due to welded sleeve. I have not had time to make any other adapters.

 

Both of these are blanks

 

Hand held

 

day time blast on mono/bipod

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My gun came already assembled , but I believe it has a M2HB bbl in it ( feels like it anyway ) . Too heavy to shoulder fire , recoil not withstanding. Did shoot some from the bench using those blue blanks. The recoil from full loads caused the original front mounting block to shake loose so , because of the big hole in the bbl and zero chance of bring her back to 57mm , I made and welded a one piece steel block to the bbl. I then cut down the length of the cheek pad bracket and bolted it to the new block. This gives me a solid mount forward for recoil. The block was welded to be sure to allow the rear mounting block on the tripod to float in the box through it's movement range . This keeps the rear mount from becoming a recoil lug and prevents the screw from busting from rearward forces. All the force through the rear mounting is vertical , down threw the elevation screw and the 57 tripod is all steel , no brass parts.

The gun is in no danger from flipping. The recoil just lifts the front feet clear. Offset recoil forces will then rotate the whole assembly around the rear leg ( pivot point ) an inch or so , then put her down.

I know a suppressor eliminates a lot of recoil , some due to the gas shearing of the baffles . That's why I'm thinking a baffle ahead of the bbl muzzle but inside the 57 tube might reduce it a little.

Chris

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