40mm XM (40x175R) VRFWS pre-Bushmaster

175mm tall
42mm mouth ID (
44mm mouth OD
48mm OD above rim
53mm rim OD
3mm rim height

The anodizing on case mouth is good, so I don’t think the case was trimmed to length afterwards.
Headstamp is “40MM XM 8-64 LOT LMC-1-2”… better picture below from bdgreen THanks!


Possibly an unfinished case for the experimental 40x175R VRFWS (Vehicle Rapid Fire Weapon System)? ECRA Caliber Data Viewer lists this with the XCR code 40 175 CGC 010, and references ECCC Bulletin 235/6, but I don’t have a copy of that available to check. The measurements seem right except for the case head, but if it’s unfinished then that would make sense. The headstamp drawing they show looks very similar as well, and includes “40 MM XM” but no lot/date info.

As the case is already anodized and painted it appears to be a finished case no?

It is time to invest in some 12" calipers…

That’s what she said??

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So the ECRA cartrige is SR or rimless, but is same mouth diameters and length as my rimmed round. Would love to see a picture of the actual round.

ETA:
Thinking about what EOD and TwoAZ said, I found this, which, if my case is not completely formed, would be around step E. However mine is headstamped and anodized. It has not been trimmed to length after anodizing.

Or the case in question is simply one of the experimental types for the one shown in the document.

Over the years I’ve found two, one with a lightweight multipiece projectile. One case has Lot LMC 1-2 8-64, the other LMC 1-3B 9-64. Several years ago I spoke to Bob Hawkinson, he had seen and recorded the case in his artillery case database, he said that he had seen the projectile before with the case and was sure that it belonged, but had no additional information. I have found nothing else yet either.

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Wow, thanks! That is awesome.

I looks like this is indeed from the Bushmaster program (or more accurately era). I tracked down the ECCC article by R. Gerber, which was referenced in the ECDV entry for the rimless version of this round. Here’s a summary:

During the development of the VRFWS/Bushmaster gun, there were concerns that the 25-30mm cartridges under consideration wouldn’t have sufficient range and terminal effectiveness. As a result, this 40mm cartridge was created in-house at Picatinny Arsenal as a potential successor.

The intent was to use a rocket-assisted projectile. Solid aluminum projectiles, matching combat projectiles in weight and configuration, were loaded for testing. Other projectiles were designed but apparently never manufactured.

The cartridge was eventually deemed to large and bulky for the intended use, and it was abandoned. It was never given an official model number.

Apparently there were three case types created during the program: rimless (as shown in ECDV), rimmed (same dimensions otherwise, as shown above), and a shorter bottle necked case.

I wonder if this is the type of (or similar) projectile they tested?


Link to DTIC

Can you pull the projectile out and show us the base ?

Measurements? (I’m gonna 3d model it)

I spent last night modeling a projectile for it based on bdgreen’s document that had a “proposed”. I even modeled in the rocket chamber but the rest of it is solid. If USSub’s version turns out to be interesting below the driving band I’ll make one of those too.




image
image

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It doesn’t disassemble, and the three holes in the bottom look suspiciously like nozzles. There are some etched markings on the bottom that look typical of test assembly markings.

Given the size and dimensions of the projectile and this in an aluminum case which is not made for high pressures nozzles make sense.

image

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