XM 40mm cartridge ID assistance

[US-Subs]

I've had this projectile for years, got it from an EOD guy on a Navy base. I was never sure what it was, it has the appearance of a projo, but it is very lightweight. For a while I suspected it might be the nose to some small rocket. It is 40mm in diameter, it has a lightweight alloy base with three webs like a peace sign, and three matching holes and recesses. It has a formerly glued on windshield over the nose and while it feels hollow I cannot remove the base. A few weeks ago a friend that had seen this item came by, he had found a similar item in a case, with a spare case which he passed to me. His projectile was solid, one piece and annodized blue. Otherwise the profile matched mine perfectly. His base is solid like a normal projectile (square base). The rotating bands are identical. While very different in construction they are clearly the same item. No stamped markings on either projectile.

The cartridge case is 40x175, with a rim diameter of 54mm. The headstamp is in two lines, top and bottom both upright - from 9-3 oclock on the top:
40mm XM 9-64
From 9-3 on the bottom:
LOT LMC-1-3 followed by a stencilled "B"

Any information or thoughts would be appreciated.

 

[SG500]

Nice bullet US-subs. I've been offered two of the complete rounds with the blue projectile over the last year, never seen the capped projectile you have but based on the blue ones I've seen its almost certainly the right case for the projectile you have. I don't know any more info about it.
Dave.