Possible improvised mortar round

[Doug]

Hi

The museum where I volunteer has several odd shells. The shell itself is clearly identified as a US 75-mm M1, but the attachment at the base is the mystery. It is very crude and would probably rattle nicely up the bore.

Current conjecture is that it is an improvised mortar round...

Thanks

Doug

 

[EODSFC]

Doug

This is the likely weapon system. http://en.wikipedia.org/wiki/File:75_mm_mortar2.jpg

The design features of your mortar are nearly identical other than diameter to the US 4.2" Spin Stabilized mortar. You can see in the picture the rifling. I suspect the copper band at the bottom is a protective cover. The 4.2" has pre-engraved rotating band.

 

[HAZORD]

U.S. 75mm Experimental Mortar from 1929

I have attached photos of the round for the U.S. 75mm mortar. It was breech loaded and used a cartridge case. If you go to the web site listed, the sign by the gun mentions it was the only mortar that could be fired downhill.

The projectile is dated 1929 and says 75mm Infantry mortar.

The case crimped onto the fins, where the little cutouts are made on the fins. The crimping cannelure can be seen on the case.

I don't think the yellow projectile shown goes with this mortar.

John

 

[Eodtek]

I have attached photos of the round for the U.S. 75mm mortar. It was breech loaded and used a cartridge case. If you go to the web site listed, the sign by the gun mentions it was the only mortar that could be fired downhill.

The projectile is dated 1929 and says 75mm Infantry mortar.

The case crimped onto the fins, where the little cutouts are made on the fins. The crimping cannelure can be seen on the case.

I don't think the yellow projectile shown goes with this mortar.

John

Ahh but the 75mm Mortar at the APG museum is a rifled tube which would match up to the yellow projectile.

It is quite possible that there were 2 development paths for the 75mm mortar, one fin stabilized and one spin and what we are seeing here is examples of both.

 

[nitrocellulose]

This mortar example that Doug has - I think it's pretty safe to call it a mortar now - has been cycled through a weapon. It's clearer when you handle it that the lands have been cut into the driving band. If the projectile itself was manufactured with grooves cut there would be no displacement of the copper. There would be clear grooves such as those found on the 106mm and 4.2". I have a 75mm HE Mk1 on my desk and the copper band is just as heavy as this. The only difference being that the ballistic profile and an expansion groove have been machined into it (and of course it's also a complete projectile). I've told Doug that I believe it to be a manufacturing pre-profiling stage for the driving band, but that wouldn't explain that it has clearly been pushed through the barrel of a weapon.

We've racked our brains here at work trying to figure this out today and we all agree that the US had been doing late and post war trials on some type of 75mm rifled mortar. There is no other explanation. It's possible that the gun posted earlier in this thread was the one used in those trials. To be sure you'd have to measure both the lands and grooves on the cartridge and inside the barrel.

 

[US-Subs]

This mortar example that Doug has - I think it's pretty safe to call it a mortar now - has been cycled through a weapon. It's clearer when you handle it that the lands have been cut into the driving band. If the projectile itself was manufactured with grooves cut there would be no displacement of the copper. There would be clear grooves such as those found on the 106mm and 4.2". I have a 75mm HE Mk1 on my desk and the copper band is just as heavy as this. The only difference being that the ballistic profile and an expansion groove have been machined into it (and of course it's also a complete projectile). I've told Doug that I believe it to be a manufacturing pre-profiling stage for the driving band, but that wouldn't explain that it has clearly been pushed through the barrel of a weapon.

We've racked our brains here at work trying to figure this out today and we all agree that the US had been doing late and post war trials on some type of 75mm rifled mortar. There is no other explanation. It's possible that the gun posted earlier in this thread was the one used in those trials. To be sure you'd have to measure both the lands and grooves on the cartridge and inside the barrel.

If that were correct then you would expect that it would follow at least some of the development paths of other known pieces (adopted and experimental) of the day. Either the band should be pre-engraved, which it does not appear to be, or is should be under a squeeze-plate, so that it can be dropped and then engage the L&Gs on the way out. This also does not appear to be present.

I suspect that to say "there is no other explanation" oversimplifies things a bit.

it might be nice to see some better photos, and maybe some more detail on the base and the band, as well as a clear, closer shot of the stamped markings?

 

[US-Subs]

I've been looking some more at the photo, blew it up a little in photoshop and took a better look at it, I've got to say I think that band looks completely bogus, like it was made in a garage.

The front edge is square, with no bevel, we didn't do that even in WWI. It does not appear to be nested into a seat recess, and it looks to go right to, or even around the base. And if you look closely, it appears that the band partially covers a pre-existing drilled hole in the center of the projo.

I'm not sure what this is, or if there was an experimental US 75mm rifled mortar, but this round looks pretty cobbled up to me. We experimented with a lot of stuff, but we did better work than this.

 

[nitrocellulose]

I agree with both of you guys completely. I also believe that this, although appearing to be fired, is a very rudimentary, possibly very early mock up of this type of ammunition.

From handling it myself I can tell you that the copper band is a typical driving band. It does extend past the base of the M1 projectile. Yes it is squared off at the both edges, but if you look back through some of the trench-made Stokes mortar bombs they weren't really much different. When you look at all the evidence, past mortar designs, etc...this is clearly a BL mortar. I can't see it being anything else despite it's clear design flaws.

R&D of A&E is a pretty complex process and I imagine that it was the same back in '48 when this M1 was machined. I'd be curious to find out who the machinist H&B is and what, if any, role they played during WWII and in post war development.

This is a pretty good history lesson. I am very curious to find out more about this. Simply because it's weird.

 

[HAZORD]

Yes, the stokes had a larger diameter at the base, but there was also a large diameter at the front end to keep it going straight down the bore. As I said in my other post, the band is too wide, and the projo will pitch and yaw around in the bore as it travels, and it will tumble when it leaves the bore. As Jeff says, we do better work than that, and we actually know what won't work.

 

[BOMBSaway1980]

It's possible it's real I asked around and someone found an article in THE FIELD ARTILLERY JOURNAL - JULY - AUGUST - 1932 THE FIELD ARTILLERY JOURNAL - JULY - AUGUST - 1932 About a stokes brand 75mm HE mortar round that could be fired from any 75mm gun.

 

[US-Subs]

I agree with both of you guys completely. I also believe that this, although appearing to be fired, is a very rudimentary, possibly very early mock up of this type of ammunition.

From handling it myself I can tell you that the copper band is a typical driving band. It does extend past the base of the M1 projectile. Yes it is squared off at the both edges, but if you look back through some of the trench-made Stokes mortar bombs they weren't really much different. When you look at all the evidence, past mortar designs, etc...this is clearly a BL mortar. I can't see it being anything else despite it's clear design flaws.

R&D of A&E is a pretty complex process and I imagine that it was the same back in '48 when this M1 was machined. I'd be curious to find out who the machinist H&B is and what, if any, role they played during WWII and in post war development.

This is a pretty good history lesson. I am very curious to find out more about this. Simply because it's weird.

Is the hole previously mentioned confirmed as being there (not just a spot on the photo)? In my experience nobody puts a band over a hole in the body, then or now, and this would give a strong indication the band was manufactured and put in place after the hole was drilled, by someone else, to make the round look good. That someone stuffed it in a breech someplace doesn't necessarily confirm anything, perhaps just the opposite. The forward portion of the projectile does not look as though it has been fired.