ID help needed


Hello all,
Got this from a friend and have no idea what it is.
HS: IVI (12 o’clock), 71 or I ( 6 o’clock)
OAL: 2.474
Cl: 2.247

Belt: .31
Case Base: .295, case tapers to .274 and then necks to .245
Bullet: .231, there is green plastic over bullet
Case and bullet are slightly magnetic. Primer recesses .04. Primer pocket is .168. Came in a black plastic belt link.


Looks like a 5.6x57B XM645 flechette cartridge. Can you snap a pic of the primer and belt link?


Rookie; Your cartridge is a 5.77mm (one box label says 5.8mm) XM645 Flechette round made by Industries Valcartier, Inc. in Canada in 1971. It has a 10-grain flechette with a green Teflon coated sabot. Some of these have a D A headstamp for Dominion Arsenal, which was acquired by Valcartier. HWS Vol. III, page 326.


Thank you for the ID. This forum is great.



What gun was this fired from.


Here is a sectioned round.



One of many experimental cartridges for experimental firearms from the SPIW (Special Purpose Individual Weapon) R&D program, for a quick review there is a series of articles from Small Arms Review:

The 5.6x57mm XM645 cartridge is pictured in the image gallery accompanying the second article.

These 3 articles were written by R. Blake Stevens who co-authored the book The SPIW The Deadliest Weapon That Never Was which provides an in-depth history of the SPIW program.


About 35 years ago I was given 6 new unfired SPIW cases that came from a brass foundry where several hundred pounds or so of these cases had arrived for melting down.


Thanks to all for the great info.