6mm SAW Cartridges

The conventional wisdom tells us that the 6mm SAW (Squad Automatic Weapon) cartridge was developed starting in 1971. Yet, there are steel cases headstamped FA 67, both naked steel and with a varnish protective finish. These cases are usually found empty, either primed or un-primed.

Q - Has anyone seen an authentic FA 67 loaded cartridge with the steel case?


IAA member Dan Nolan has collected SAW rounds as long as I have known him; but I do know think he is a Forum follower. I will try and ask him

I believe that I mentioned before that I’m editing, including formatting, History of Modern U.S. Military Small Arms Ammunition, Volume III by Frank Hackley, Bill Woodin, and Gene Scranton. I have read the entire book several times, and it is progressing toward completion in the not-too-distant future (don’t ask; I have no idea when it will be done).

Chapter 12 (of 21) deals with 6mm Squad Automatic Weapon (SAW) ammunition. A quote from the chapter’s first couple of paragraphs and a later one follow:

"The ammunition for the 6mm Squad Automatic Weapon system would prove to be the last full scale small caliber development program carried out at Frankford Arsenal before the Arsenal’s closing in 1977. The user requirements for this new weapon included terminal effectiveness parameters at 1000 meters which exceeded the performance capabilities of the standard 5.56mm. Accordingly, a new caliber or a more powerful 5.56mm cartridge was envisioned.

Development work started at Frankford Arsenal on a cartridge for the squad automatic weapon during July, 1971, when a computerized Parametric Design Analysis (PDA) was started to determine the ammunition concepts to meet the SAW user requirements. Five candidate designs - 5.56mm, 6.00mm, 6.35mm, 6.5mm (all using conventional jacketed bullets with steel or lead core) and a 6.5mm steel flechette concept were initially studied. The refinement of these efforts during August, 1971, resulted in the concentration on two calibers: 5.56mm (.224 in.) and 6.00mm (.243 in.). This was the first use of a math model for small arms cartridge design, the printout of which gave data on basic design parameters such as bullet weight, bullet length, barrel length, muzzle velocity, chamber pressure, basic case dimensions, systems momentum, weapon weight, etc.

… The initial production of steel cases were headstamped F A 7 2 and used a 0.130-in.-thick steel strip with an 875 degree temper. The case was protected by a phenolic varnish finish previously developed at Frankford Arsenal during 1967-1971 for the 5.56mm and 7.62mm steel case programs. During December, 1972, the Pitman-Dunn Laboratory experimented with an extrusion process for forming the 6mm steel cases. To identify these, a modified 5.56mm steel case heading bunter (F A 6 7) was used. About 100 were loaded into ball rounds for tests."

Frank explained to me in an email today that while he was at Frankford Arsenal (as its final Commanding Officer), the late Dave Hughes, author of The History and Development of the M16 Rifle and its Cartridges, visited the Arsenal and located some scrap (F A 6 7) cases in various stages of completion, which is probably the source of these.

Hope this helps answer the question.


Many thanks for posting that. I usually go directly to Col. Hackley with questions like this but I have been pestering him so much lately that I feel I’m overstaying my welcome. I keep all of his emails in a binder and it is beginning to look like a condensed version of Vol III. ;)

Bill Woodin wrote an article on the 6mm SAW Cartridge Development some years ago and much of the above was in it. The one thing missing was the paragraph on the steel FA 67 cases. Now, we all know.

Quite a few of those FA 67 cases made their way into collectors hands but, unfortunately, there were so many of them that a lot ended up in the garbage. I managed to get a couple but the supply seems to have dried up.

We are all going to owe HWS big time when Vol III comes out. I understand it could be as soon as the end of the year. 600 pages! That should keep us busy digesting all the new information for a long time. Or, at least until Vol IV ;) ;)

Thanks again


I don’t collect 6mm SAW cartridges except for a few representative examples. But, if you are so inclined, here’s the '67 headstamp to look for.


Excellent information! I had always wondered why that headstamp existed when development didn’t start until the early 70s.

Here’s the specimen that I have, unfortunately just a primed empty rather than a loaded round. Ray, is your case plain steel?



Chip - Yes, just plain steel. No protective coating of any kind. The fellow that gave me this one said he had a “bucket full” of them years ago but finally tossed most of them because he had no use for them and they were taking up valuable shelf space. Some collecors would say that was a good thing because it made them that much scarcer for the few of us that collect such things. I can see the logic in that, but confess that I’d have a hard time throwing away any experimental cases. I don’t even like throwing away a 30-30 case.


I have a loaded 6X45, steel cased, FA 73, round given by a friend in 89. The case has red primer seal, and dark finish similar to steel cased 7.62. I pulled a case length of 1.768" and OAL of 2.577", with bullet dia of .2435 at crimp groove.Don’t know where it was found, but does look to be original factory load. Did this round have a modle number?
Also have 6X49.5 round with anodized aluminum case, no head stamp, red primer seal. Case length 1.952", OAL 2.758" and bullet dia was again, .2435. Any info on this round? Thanks for all the SAW info, Tom.

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You have a couple of the many variations of the SAW cartridge. The steel FA 73 round is the final iteration that was tested extensively. It is the XM732 Ball. The aluminum round is a lengthened one developed as an alternate to a steel or brass case. I’m not aware of an XM designation for it.

The center cartridge in the photo below is one submitted for test by the Brunswick Corp.

None of the 6mm SAW cartridges were adopted.

If you do a search you’ll find descriptions and photos of many of the other variations.


Thank you for the info, trying to tie up some of those loose ends with my small collection at last, Tom.

6x45mm SAW


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Mel, do I understand correctly, FA67 headstamped cartridges were actually made in 1972?
Thanks, Fede, for fixing photos (again).

Vlad; Yes, that’s right. In this particular case, the obviously “wrong” headstamp bunter was used to identify this small lot of 6mm steel cases. Frankford Arsenal didn’t really care about making things easier for future cartridge collectors. The reference (HWS Vol. III, pp 337/338) goes on to explain that about 100 loaded ball rounds were made for tests.

As an aside, FA sometimes used other “wrong” headstamp bunters to strengthen the heads of experimental cases like the aluminum 5.56. When the case head was hit hard by the bunter, that made it stronger.

Thanks. One more question about the headstamp of the 1st orange tip round. It appears that the head was hit too hard and it concaved, therefore the headstamp (I suspect “FA 73”) did not impress well. Is it just a defect or done on purpose?

Vlad, normally headstamps are made by bunters which are part of the case forming process.
There are some headstamps which are applied to readily manufactured cases but most are not, also not the one here as far as I can see. So nothing got struck here and case heads of solid drawn cases do not concave when a hs is applied later.

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So it is probably a defect. I can actually feel the curve with my fingers, it is weird.

Vlad, maybe the experts can chime in here. I wonder if the concave head was made on purpose.

There are artillery cases with such heads but the radius concaving the head is very pronounced there and it is all related to the breech of the gun.

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But my other 2 rounds are “flat heads”.

It depents much what testing was about if this here was intended.

For example I know large caliber systems which used case deformation as a way to compensate force of the forward moving breech when a round was chambered.

Also case deformation is a huge factor when a round is fired. Not that I know anything about this one here but the concave base could be part of a recoil/energy absorbtion.

As said let the experts chime in.

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The concave dish in the head is a result of the case being cold worked
This can also be seen in some 7.62 and 5.56. The 5.56 is also known with a “C” at 9 and a “W” at 3.

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