WWII 3 Inch M5 Anti-Tank Gun

[bogey1]

That cat is cool.

[ScotsGuards]

The Cat IS cool. Congratulations on a very nice restoration.

You don't see many of the towed 3 inch AT guns as the US tended to mount that gun in a modified Sherman chassis as the M-10/M10A1 Motor Gun Carriage. AKA Tank Destroyer.

[JoshIronshaft]

The Cat IS cool. Congratulations on a very nice restoration.

You don't see many of the towed 3 inch AT guns as the US tended to mount that gun in a modified Sherman chassis as the M-10/M10A1 Motor Gun Carriage. AKA Tank Destroyer.

They made 2500 of the 3" M5 and apparently that was too many. I haven't found a number but I don't think a major percentage were shipped overseas. I do know they lost around 300 in combat. The M10 self propelled tank destroyer was quickly found to be the better tool for the job in Europe and it seems they stopped shipment of the M5 at some point and they issued orders to switch all towed TD units to self propelled as soon as M10s or M18s were available. The M5 actually is one of the most common guns to see as a static display piece here in the US. I have looked at several dozen and I know where many more are on display.

[JoshIronshaft]

Time to address the nitrogen leak!

Here is the problem area, the top rear of the recuperator cylinder where nitrogen is added. Some soapy water showed the leak was coming from the hole in the middle where the nitrogen tool threads in.



The recoil rod was unbolted from the sleigh and the gun assembly was slid back using a come-along to have room to work.

I made a large spanner wrench with a three foot handle to turn both of the nuts seen.

Amazingly, both nuts turned with little struggle.

Here is what comes out:



The middle piece with the copper sided rubber seal needed a little slide hammer encouragement to pop out. Amazingly my harbor freight slide hammer rod had the same threads as the hole used to fill the nitrogen!



The check valve that is opened by the nitrogen filling tool is attached to the backside of this piece.





This little seal seems to be the problem.





The inside of the recuperator cylinder looks good, just a little crud to wipe out.



So now to order some square o-rings from mcmaster!

[JoshIronshaft]

A week ago I replaced that little seal on the nitrogen filling end that was leaking with a standard off the shelf square #206 o-ring from Mcmaster-Carr. After reassembling, refilling the nitrogen, and waiting a week to check it... it held pressure! Woohoo!

I also prepared some cases for use as blanks/salutes. I will make a separate post on those.

[GOYABEAN]

A week ago I replaced that little seal on the nitrogen filling end that was leaking with a standard off the shelf square #206 o-ring from Mcmaster-Carr. After reassembling, refilling the nitrogen, and waiting a week to check it... it held pressure! Woohoo!

I also prepared some cases for use as blanks/salutes. I will make a separate post on those.

popc1.gif

[JoshIronshaft]

Let's talk scopes, mounts, etc!

Finding the correct scopes and mounts for an ordnance piece can take a long time and a lot of hunting. Usually they are fairly affordable, as demand is not high for these things. They are just hard to find.

The M5 had 3 different sights.

The left side of the gun had:

- M61A1 telescope mount with M79C telescope and instrument light M33 (with one dovetail mounting lamp)

- M21A1 telescope mount (or M41A2 mount) with M12A3 panoramic telescope and instrument light M19

The right side of the gun had:

- Range Quadrant M10C and M23 telescope mount with M29A1 elbow telescope (or M29 elbow telescope) and instrument light M36

I am aware of one privately owned M5 with all 3 sights and mounts. I was able to look at it and boy is it pretty.

Here are photos from the factory that built the carriage for the M5s and assembled the guns for shipment showing the original optics:





After reading the TM I have, I'm still not quite sure how the 3 sights were utilized. I know the M79C telescope on the left is primarily for direct fire and the range quadrant on the right is primarily for indirect fire. I am not sure if the M12A3 panoramic telescope on the left was only used for indirect firing or if it was also used to support the direct firing.

Regardless... I want them!

I was able to find the M21A1 telescope mount, M12A3 panoramic telescope, and instrument light M19 without too much trouble because these were also shared with the 105mm howitzer. You can probably go on ebay right now and find these. The M12A3 telescope resides in a M27 packing chest.

The M61A1 telescope mount with M79C telescope are rarer than rocking horse poop. I was able to find an M79C from someone who picked it up at an antique store years ago. Unfortunately, someone removed the cross hairs so it could be used as a generic telescope, and the eye cup is long gone. An automotive CV shaft boot is standing in for it. What a heavy beast this is. The large and complex mount for this scope still eludes me.

Since I have no mount for my M79C, I lucked into a custom mount for an M69 scope. It was very nicely made to mount this scope on an M5. The M69 scope was meant for other guns, so the reticle would not be accurate for 3" loads, but it looks good sitting on the custom mount. The mount has no adjustment, other than loosening the mounting bolts for the whole thing and kicking it around, so it is serving as just a spotting scope. This scope is an M69F and it is complete with various filters in a T16 carrying case. It was last inspected in the 1950s per the tags in the case.

I haven't even caught a whiff of the range quadrant sight on the market. The elbow telescope for it is common, but useless without the main part. I may have to adopt one from a 105mm howitzer if I want to have something mounted, but the sight would not be accurate for 3" loads.

Here is what I have:









The M19 instrument light is really cool.



It throws light on your dials, the two spirit levels on the mount, and lights up the reticle inside the telescope.



The reticle is uniformly illuminated, but this is the best photo I could take.



I also like this little iron sight on the telescope.



Here is my M79C aka T116 telescope.



It also sports a little iron sight.



It is tough to hold out with one hand. You can see the large mounting points on the bottom and the slot for a single dove tail illumination mount to light up the reticle it would of had.

[Emptymag]

I don't even know where to begin. Just "wow" - awesome stuff.
Thanks for taking the time to share it all!

[JoshIronshaft]

Happy to share. It would be selfish if I kept this all in my head.

I just find all of this stuff to be terribly interesting and I figured some of you would too.

[Emptymag]

I'm always fascinated by the amount of work and material that went into the most simple of things like the cases those optics were placed into.