.50BMG/10mm case

Someone posted this on another forum. Apparently the headstamp is “T W 4 3”. Has anyone ever seen one before?

Hi Falcon,

can you pls give me the link to this topic in the other forum


Here is the link: bocn.co.uk/vbforum/oddball-case-t27092.html

THX !!

wasn’t aware of that one yet


Speaking of necked-down 50bmg casings, have you ever seen one of these ridiculous things:

It’s a 50bmg necked down to a .17 Sorry about the fuzzy image, I captured it from an auction which went unsold. The seller wanted around $40.00 for it.

I once saw a .50 necked down to a phonograph needle! It was a beautiful job too, with nary a wrinkle in the shoulder. What a lot of time spent on a joke.
Oops, do you young guys (Jason, Falcon?) know what a phonograph needle is?
Just teasing you.

What an awesome cartridge is that John! Very effective against…eeeeh… against what? Boys Town Gang LP’s? :-D
But it defenitely would not deface my collection!

Hey guys, I realize that the cartridge shown was intended as a “joke” but there are places in our hobby for those things too. Beauty is in the eye of the beholder. I would hope that none of us ever become cartridge collector snobs.

And don’t be so quick to scoff at the idea of a phonograph needle for a projectile. The U.S. government spent years and millions of dollars in trying to perfect just such a thing. They approached it from a different angle, using a sabot to hold and guide the flechette rather than trying to manufacture a 7 caliber rifled barrel.




I can’t say that this will lead anywhere productive, but the US experimented with a 50-30 High Velocity cartridge during WW II. There were at least two case iterations and the T5E1 looks very much like the one pictured.



Well after WWII, the AF was experimenting with what I think was called the GAU-1 which was a 10mm weapon based on the .50 Browning case head. The early cases were tapered and the later ones were straight case for more capacity. I have seen one of the early tapered cases made by silver soldering two WWII .50 cases together because the case length was too long to just resize a .50 case. The GAU-1 was originally intended for the F-15 (2 gun installition) for an very high velocity weapon which significantly increased the gun engagement envelop. Very early in the F-15 design, the GAU-1 was dropped in favor of the GAU-7 which was a 25mm fully telescoped, consumable case weapon. When this program got in trouble it was dropped and an M-61 gun was installed, significantly reducing the gun envelop from what was originally envisioned.

The GAU-1 project was clearly based on previous work, and perhaps this case was part of that. At least I found the 10mm caliber interesting and thought I’d share the GAU-1 info with you.

Lew, the 10mm/.50 6-barrel rotary was the GAU-6. It’s described and illustrated in Chinn Vol 5 pages 125-127. It was in fact made in .50 cal first to test the gun, and they never got around to making the intended 10mm version because of problems with the ammo development. There is no direct relationship between the GAU-6 and the GAU-19/A.

Several variations of the 10mm/.50 were made, but they looked nothing like the one at the start of this thread. They had longer cases, of around 107mm. Below is a pic which includes the 10x107 XM277 in my collection (headstamp F A 61). You can also see a .30/50 in the same pic.

Thanks for all the replies on the case. Unfortunately it isn’t mine.


I also had an earlier version of the 10x107mm that had a tapered case. It was a black case dummy that I think I traded long ago to Warner Schalterbrand for a 9mm. I got it from an old engineer at Eglin AFB in the Lab. I also saw an even earlier version of the 10x107mm round that was in the office of Dale Davis who ran the Gun and ammo directorate in the Lab. This two piece case was made from two .50 browning cases to get to the 107mm. I did not compare it to my tapered case 10x107 so I don’t know if they were the same case profile or different. Somewhere I had some notes on this cartridge development, but they have been lost or buried in 30 years of moves.

Cheers, Lew