OCSW ammunition

A search shows up very little on this ammunition so I hope no-one minds if I add this;


That was the original ammo series for the GD XM307 (cancelled around 2007 IIRC).

ATK subsequently modified the ammo for its LW25 Chain Gun, with slightly heavier projectiles with a more conical nose (see display dummies below). This one seems to be dying due to lack of interest.

There is also an AMR project for this caliber:

I added this one to my collection recently. Can anyone identify it?

What puzzles me is that the projectile is very different from those usually seen in this calibre: it is significantly shorter and more pointed. I understand that it may have been developed specifically for the Barrett rifle. Can anyone confirm this and provide more information? The only marking on the round is the faint stencilling on the case which seems to read as follows (some of the letters/numbers cannot be clearly made out – my best guesses for these are shown in standard instead of bold text: USE05D00. 006

Tony, is this the 59mm case?

Yep, I’ve just remeasured it to be certain: 59mm it is. Overall length is only 120mm compared with 140mm for the current ATK rounds. The projectile is firmly crimped in.


According the MIL-HDBK-1461A from 1999, the USE code is most likely “Piper Impact Inc., New Albany, MS” (that was the only active mfg with that code at the time)
the first 2 numerical digits is the year of mfg: 2005
The D on position 6 is the month of production: April
last 2 groups of the number are lot-codes

Thanks for that.

Anyone have any idea why this projectile is so much shorter than the others?

Tony is the XM109 in the file name correct?

Hi Tony,

This round is for a Barrett rifle conversion.


Thanks Paul,

Does that mean that all of the ammo for the Barrett XM109 used shorter projectiles than the OCSW?

This is a puzzle since everything I have seen to date suggests that the XM109 used standard OCSW ammo.

I’m getting older and my memory is failing…but if memory serves (phone chat with Barrett folks a few years back), there was some interest in projectiles that could be used in both the Barrett ‘payload’ rifle and the larger systems, mainly practice pills. Like a gigantic .38/.357 ha!

As far as I know the Barrett did use shorter cartridges than some of the related 25mm candidate systems; in Barrett’s early ads you could see a large lightcolored spacer down inside their standard .50BMG magazine. Swappability between .50BMG and 25x59mm was listed in both sets of literature…maybe crew-served variants could be upgunned to a larger cartridge case or just a 59mm case with a longer projectile/OAL?

With the regards to the original picture shown…“penetrates PASGT”…gee ya think? ha.

Not sure if there’s any relevant info but I did a huge display at SLICS a few years back " No Place to Hide". Maybe search. OCSW. ACSW. Xm25 OICW there will be some threads related to all and more I can try and post a pile of photos but multiple photo imports is no easy task…at least to me

FWIW here is a brief power point presentation by ATK on the HEDP (High Explosive Dual Purpose) 25mm Barrett cartridge: dtic.mil/ndia/2004arms/sessi … ormick.ppt