US experimental ctges

What are the official names for these two ctges


Those are two of the computer designed experimental cases from the Squad Automatic Weapon (SAW) development project at Frankford Arsenal in 1971. As far as I know, they have no official names. Collectors call them exactly as you have posted, 5.56MM Special case, and 6.00MM Special Case.

The 5.56MM was shown on Sketch BCX-30, and the 6.00MM on Sketch BCX-1. That’s as close to an “official” designation as you’ll get, I think.


thank you Ray !

Same question about these two ones.

Lockless is the official term for the project. Nickname is “Chicklet” as the 5.56 version looks a bit like the gum

Anyone have any performance figures for that 5.56mm Special?


Only a very few of the cases were manufactured. There is nothing to indicate that they were ever loaded or fired. Test barrels chambered for the cartridge, and test bullets, have never been located.


The 5.56 mm round for the Hughes Lockless gun from the late 1960’s was named by its inventor as the “5.56 mm Full Telescoped Caseless”, besides it was obviously a “cased” cartridge. Even more confusing is that the gun was later offered as a convertible design firing also the 5.56 mm Hercules caseless telescoped round.

The one on the right is a later design offered by McDonnell Douglas Helicopter Co. for the ACR Rifle tests of 1986 and it was loaded with a multiple flechette load in a .338 or .42 caliber 2-piece sabot.

Does anyone have any idea what projectile they intended to load into the 5.56 Special?

I rendered the cartridge in a CAD program to obtain the internal volume (2.68ccs), then used a Powley Computer to get some idea of the performance. At 57,000 PSI, it could propel a 55gr bullet at approximately 3,550 ft/s. At the same pressure, it could propel the 68gr Sierra FMJ at about 3,250 ft/s.

Tau, the intended bullet was a lead core 68 gr.

It wasn’t the same 68gr bullet studied in the early SCHV tests, was it?

This thing:

Tau, I’m afraid that nothing else is known about the intended “lead core 68 gr” bullet.


What about these two ones ?

The one on the left is a 5.7 Melvin M. Johson (MMJ).
Is it an experimental or a wildcat ?

The one on the right I don’t know the name.


The 5.7 Johnson (AKA 5.7 Spitfire AKA 5.7 MMJ) was a .30 Carbine wildcat designed by Melvin Johnson, the same person who designed the M1941 Johnson Rifle and LMG, and who was a significant contributor to the design of the AR-10. The cartridge was intended to be used in an easy rechambering of existing M1 Carbines, for use by police and paramilitary forces.

The other cartridge might be the .22 Aberdeen Proving Grounds Carbine cartridge, which was also used in M1 Carbine conversions, as an early testbed for the SCHV concept.

Cartridge drawings and photographs of both can be found at and

thank you Tau.

I had the two same rounds in my collection referenced on two different names !!

I’ve learned the name of the other one (22 Aberdeen ctge carbine) but I thought there was an official name.

What is the official of the two ctges on the right ??

The cartridge third from left appears to be a drawing of the prototype for the .221 Remington Fireball, a high velocity cartridge intended for a single shot handgun.

The last cartridge from the left is the .22 SCAMP, a cartridge also intended for a pistol, though in this case it was a high capacity semi-automatic, intended as a 1911 replacement.

The .221 Fireball is a fairly common varmint cartridge today, while photos of the .22 SCAMP can be found on

Thanks Tau

  1. Is there an official designation for 22 Scamp ?
    (I have all the photos of these ctges because they are pictures of my collection)
  2. Where is the a difference between a regular 221 and the prototype one?
  1. It was a Colt in-house project. I believe it was just called “.22 SCAMP”.

  2. I am unsure; I honestly do not know that much about the .221 Fireball. Most factory-designed cartridges undergo a few changes before they hit market, and since your case dimensions are somewhat different than that of factory .221 Fireball, but very close, I guessed that it might be a prototype.

If you drew those yourself, then it’s also possible that it’s just a factory .221 Fireball that’s at the edge of the dimensional tolerances.

The 5.7mm MMJ or Spitfire conversion for the 30 Carbine was offered commercially for a while in the early 1960s. I really, really wanted to have my carbine modified, but just couldn’t afford it on a SSgt pay with a family!

The .22 Carbine program was a project of Dave Perrin who worked at Aberdeen for many years. I don’t know if he was the official project manager, but he told me back in the 1980s that he did the work on the 30 Carbine.

As far as I know, the only US military use of the .221 Remington Fireball was by the USAF in a project at the Armament Lab at Eglin AFB. They produced 4 or 5 selective fire, bull-pup, survival weapons in this caliber. One was subsequently modified for use of a silencer and was adapted over time for three different .30 caliber cartridges, one based on the 30 Carbine and the other two different case shapes using the 5.56mm case. To reduce weight, Remington also developed a plastic case version with a steel head and a sabot .17 caliber bullet that was the origin of the Remington accelorator line of bullets. The original fireball ammunition came packed in 5,56mm stripper clips in a single 20mm ammo can. Each clip included 2 or 3 unmarked tracers. I wound up with this can and the residual ammo from the testing. The bullets were standard 5.56mm bullets.

Others in DOD may have also tested the .221 Fireball, but this is the only use I have ever heard of.


I didn’t draw the ctges myself, bt it was my friend Jacques Barlerin
He used to draw very well and this ctge is 100% sure a military one.
I must have somewhere a xeros copy of the label

I don’t have anymore a regular 221 to compare dimensions, it because of that I am asking the differences

has this one the good name or is it a test barrel ctge?