ACR trials ammo designations?

I have two US rounds in my collection from the Advanced Combat Rifle trials of the late 1980s. One was used by the Colt competitor and is a conventional 5.56x45 case with a duplex loading (two short bullets stacked one on top of the other). The other round is for the AAI candidate, it also looks like a standard 5.56x45 case but the visible projectile is a plastic sabot for the flechette buried within the case.

Can anyone tell me what their designations were (assuming that they had any)? Also, any other information such as projectile weight and muzzle velocity?

The AAI ACR 5.56x45mm cartridge fired a 10.2 grain flechette at 4,600 fps. The final Colt/Olin Duplex round fired a 35 grain (forward) and 32 grain (trailing) projectile at approximately 2,900 fps.

Thanks for that. Were they given XM numbers?

These are my four Olin rounds from the ACR trials together with the titles as taken from their respective boxes;


5.56 Full Caliber Duplex Ammunition Phase II Test and Demo Rounds Loaded 3-23-88

5.56MM Duplex Phase III Colt Test Rds, Handloaded, Rear Bullet FAB 10-88

5.56MM Duplex Phase III Colt Test Rds, Loaded 12-23-88

5.56MM Duplex DAAA21-88-0867, Phase III


Tony: As far as I know, they never went far enough to warrant XM designations. The ACR ammunition development had been the responsibility of the individual rifle manufacturers. I suppose that if the Army had actually chosen a winner for further development, then they would have assigned designations for the rifle and its ammunition.

Thanks again, gentlemen.

I believe the “XM” system of designations was discontinued with the closing of Frankford Arsenal in 1977. If the ACR cartridges had official designations they would have been patterned after the LCAAP system.

Unless I’m wrong.


I’m pretty sure you’re wrong, Ray. For example, the 7.62mm M993 AP round was originally XM993, according to info I received from Picatinny several years ago.


As more evidence, the M855 and M856 were previously XM855 and XM856.

OK, I said I could be wrong. But it’s not fair to leave me hanging.

What are the dates of the XM855 and XM993?

What year did the XM series end?

What is the LCAAP system?


I didn’t keep any of the correspondence from Picatinny, so can’t give you a precise answer, but I think the Bofors AP round was type-classified as XM993 in the mid-1990s.

I think the XM855 dates from the late 70s so maybe it was one of the last numbers assigned by FA? Possibly, LC continued the series for some time after they took over?

Another question. Do the numbers assigned and used by LCAAP carry the same “official” weight as they did under FA?

Inquiring minds (me) want to know.


LCAAP executes “projects” or “programs” as assigned by the Army at Picatinny, so the XM designations come out of there, rather than LC. XM designations continue to be assigned even today. The latest designation I’ve seen from the NDIA Small Arms Ammunition group annual presentations was “XM1116, Shotshell, 12 GA, Extended Range, Non-letahl.”

Some other recent ones that might be of interest…

XM1002 Cartridge, Caliber 120mm, TPCSDS-T
XM1006, Grenade, 40mm, Sponge
XM1007 Cartridge, Caliber 120mm, ERM-TERM (Extended Range Munitions-Tank Extended Range Munition)
XM1018 Cartridge, Caliber 20mm, OICW High Explosive Airbursting (HEAB)
XM1019 Cartridge, Caliber 25mm, OCSW High Explosive Airbursting (HEAB)
XM1037 Cartridge Caliber 5.56, Short Range Training (Tri-Nose Fin).
XM1040 Cartridge, Caliber 105mm, APERS (Canister)
XM1041 Cartridge, Caliber 9mm NATO Close Combat Mission Capability Kit (Paintball-Pistol)
XM1042 Cartridge, Caliber 7.62 NATO Close Combat Mission Capability Kit (Paintball-Rifle)
XM1047 Cartridge, Caliber 25mm, OCSW Blank
XM1049 Cartridge, Caliber 25mm, OCSW AP
XM1050 Cartridge, Caliber 25mm, OCSW TP
XM1051 Cartridge, Caliber 25mm, OCSW TP-S (Target Practice-Spotter)
XM1060 Grenade, Caliber 40mm, Thermobaric
XM1071 Cartridge, Caliber 7.62 NATO Close Combat Mission Capability Kit (Paintball-SAW MG)
XM1111 Cartridge 120mm, Mid Range Munition (Guided)

Well, I’ve been duly educated. It appears that the old ways of Frankford Arsenal and Springfield Armory are indeed dead and buried. Does this apparant trend portend the end of experimental/prototype military cartridge collecting as we know it today? It’s hard for me to envision something such as HWS Vol IV.