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A friend and I spent the last several years restoring this 1942 US WWII 3 Inch M5 anti-tank gun (ATG) to functional original condition.
It is a registered destructive device/NFA item, capable of sending projectiles down range. Inert projectiles only. Explosive projectiles would be individual DDs by themselves and we're not going down that path.
It's not 100% complete but it's finally to the point I can show it off. It's taken a lot to get to this point. There is a small community that supports these kinds of projects and their help has been greatly appreciated. The amount of things I learned and people I met through this journey has been incredible.
A common question is, "Where did you get it?". Many large bore guns like this are legally in private hands. They are bought and sold just like any other NFA item. There were some towed guns in the last Rock Island Auction. Usually they are bought and sold by word of mouth.
3" Mk II M2 brass cases and 3" (76mm) projectiles are not too hard to find, but spendy. Cases average $150 and projectiles vary from $60-$300 (depending on condition and collectability).
Smokeless artillery powder is regulated since it not used in small arms and obtaining it is a process. I have to give some thanks to the local ATF office for answering all my questions and providing guidance on how to do this all legally. The PA DEP is also tied into the regulation of the powder. They have been good to deal with as well.
The case has a primer and primer extension tube that protrudes deep into the case. These can be reloaded with new primers.
A blank salute can be fired by putting black powder in a case with no projectile. I will have dedicated cases for that with a simple primer set up.
I have found one of three original sights it was equipped with (for direct and indirect fire). I am still working on finding the rest of those and other original accessories like cleaning rods, etc.
The only modification from original is modern 12V electric trailer brakes and a modern 7 pin connector to replace the original electric brakes. Yes, in 1942 they had electric trailer brakes. They were only for breakaway situations though.
Test fire will be soon. The fun is just getting started.
First time out for a test ride (almost forgot the safety chains).
Saturday we displayed it for the first time at a local club event. Weighing in at 5,700 lbs, it takes at least 4 or 5 strong guys to move it by hand. The Army assigned it a crew of 10 soldiers.
It is not fun to tow. No suspension, weight balanced on a single axle, very little tongue weight. Very bouncy even with the tire pressure lowered. Anything further than a short drive from the house and it will go on my car trailer for transport.
The barrel mounted taillight is an original accessory. Yes, that is an expanding PVC test plug in the barrel for transport.
Here is a poster board I put together for display. Large photo, there is more to the right which may not show up on mobile device unless you turn your device sideways.
Cleaning a 150" long barrel with a 3" bore is a lot of work. Hours of work. The first cleaning to see the condition took about 4 hours.
A t-shirt makes a perfect cleaning patch.
Beautiful rifling.
Restoration process photos...
We replaced a lot of rusted out metal.
The modern brake backing plates only needed a little modification but I had to design drums for the hubs that were machined from solid steel.
The majority of the right trail leg was replaced due to rust.
Every part was cleaned, repaired as needed, and prepared for assembly.
This assembly with two heavy duty coil springs counter-balances the weight of the gun. You can see them under the back of the gun when assembled.
Those two springs are reproductions, made by the company who made them during WWII using the design specifications from the original US Army order.
Even small parts like this brass latch handle took hours to braze back together.
