XM156 uses? vs. M48A1?

There is a lot of information on the M48A1 (shorten .50BMG) cartridge uses as a spotter for the 106mm BAT artillery cannon.
I have been trying to research the use of the the XM156, a regular length 50 Caliber BMG case with what looks to be loaded with the same projectile was the projectile* on the M48A1 cartridge. ( *My specimen of both XM156 and M48A1 projectiles look the same)
I have found very little on the XM156 history or use, and am reaching out to the military experts.
below XM156 and M48A1

Many thanks in advance for enlighten us all.

Dave, did you manage to compare pulled porjectiles of both?

I take a picture shortly of both side by side and post
Looks to be the same projectiles.

Looking forward to that, thanks!
But once you are handling them, could you weigh them as well?

I figured out the mystery on my XM156 cartridges as I bough a 50BMG tin full of them a few years ago at a show.
I just notice different head-stamps of older 50 cases FA 54 , RA 43on my XM156 cartridges, however these cases still have a crimped primp on them ?
Which leaves me to believe they may have been produced by pulling the original projectiles of these cartridges and replaying them with M48A1 projectiles., or the were reloaded where the primer was crimped again, if that is possible?
I guess the guess on is did the military us the XM156 or is the XM156 a commercial idea ?

The XM156 was an experimental long range spotting cartridge for the Shillelagh 152 mm gun and was used with the XM121 machine gun. Bullet is a regular M48A1.

An interesting characteristic of this cartridge is that it has a unique case type with slightly different dimensions than the standard .50 cal. case.

The only authentic headstamp is F A 60.



Then it appears my cartridges are a commercial version of the XM156 using older cases loading with the M48A1 projectiles, which solves that question, as my cases are normal 50cal BMG cases.
Thank you for the help.

Dave, I don’t know if there was/is a company offering commercial loads using spotter bullets, but a .50 cal. shooter may have loaded these just to have some fun. CDVS is a well known source for this kind of components.

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These spotter rounds are commonly reloaded for use in M2s and other .50 cal rifles. For some reason there seems to be a large surplus of the projectiles. They make a fun round to shoot.

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All of the .50BMG sized loads I have seen with the spotter projectiles have been reloads done for aftermarket sale at gun shows, Knob Creek, Big Sandy, Gunbroker, etc… I wouldn’t be surprised if a great many of the shorter B.A.T. cartridges were pulled down (carefully) to retrieve these projectiles to that end. There did seem to be a relatively odd number of available surplus spotter projectiles for people to do this sort of loading over the past 20 years or so. They should run thin sometime over the next 10 years I would presume, since the internet has made out-of-the-way local sellers across the U.S. more accessible to buyers anywhere, and these oddities get gobbled up.

Matt, I agree, however, at least thanks to Fede we now know the original reason for the XM156 cartridge which was the reason for this posting.
To quote Fede (above): “The XM156 was an experimental long range spotting cartridge for the Shillelagh 152 mm gun and was used with the XM121 machine gun. Bullet is a regular M48A1.”
Also only originals XM156 have the “FA 60” Head-Stamp although it would be easy to fake if you have the “FA 60” cases and have the ability to load the M48A1 projectiles.