6mm SAW (Squad Automatic weapon)

The 6mm SAW (Squad Automatic Weapon) prototype cartridge selected for further development by Frankford Arsenal in 1972 was unlike anything in service at that time. The case had a head diameter of .410", larger than the 5.56 x 45 but smaller than the 7.62 x 51. The bullet diameter, 6mm, had not been given serious consideration before. To provide superior external ballistics and terminal effect, and sufficient room for an adequate tracer element, the bullet was very long for it

Excellent stuff Ray!

I can post pics of the following if it’s of any help/interest;
6 x 45mm SAW Dummy
6 x 49mm (Long case) SAW Dummy
6 x 46mm SAW Contender


Jim–Please do post images of what you have. As with so many of Ray’s posts, they end up being small research files on the subject.

Ron/Ray…and anybody else interested!
From (L) to ®;

6mm x 45mm SAW Dummy. This has an inert filling and an inert primer. Hdsp is ‘F A 7 3’.

6mm x 49mm SAW Dummy (Long Case) Anodised aluminium case, inert filling and inert primer.

6mm x 46mm SAW Contender. An independant venture by the Brunswick Corporation in an attempt to get in on the SAW project. Note it’s jacketed soft-pint bullet.

The disintegrating belt links for the SAW are not uncommon but are frequently mistaken for 5.56x45mm M27 type links. The SAW links are a different size and shape (but not a lot) and are usually stamped 6MM S or something similar.


Mine are stamped 6MM BRW (whatever that means). They may be similar in appearance but they do not fit a 5.56x45 very well.


BRW typically indicates Borg-Warner.

Thanks Daniel. That looks about right.

Do you have a photo of the SAW weapon that you could post? I don’t have one in my photo album. It looked about like the current M249 didn’t it?

For you guys interested and who want to expand your horizons, be sure to read Tony Williams’ excellant article Assault Rifles And Their Ammunition.


Thanks for the topic, Ray. Your plan worked. I want to know more…

I’ve always thought th 6x45 was kind of neat and spoke to some of the deficientcies of the 5.56. Also have wondered why the idea didn’t take off from the 6.35 experimental case size from the late '50’s rather than the notch smaller diameter case used.

That said, the WCC 73 headstamped 6x46 Brunswick shown by Jim looks to be smaller in the photo as far as case dia. Is that a 5.56 case used or something else?

Also, are any 6x45 found in aluminum?


There were three different 6mm SAW weapon designs: the Maremont XM233, the Philco Ford XM234. and the Rodman Laboratory XM235. If I had a working scanner, I’d scan some photos from my library. If I remember correctly, “Small Arms of the World, 11th Ed.” has photos of all three. The 12th edition has the longest written history of the SAW program I’ve seen in print. The January–February 1980 edition of “The International Cartridge Collector” has the most I’ve seen regarding the ammunition.

In “The Black Rifle”, Blake Stevens and Ed Ezell wrote that the SAW’s story would fill an entire book. However, I doubt that Stevens will ever assemble such a book given how poorly the SPIW book sold. In an interview, he claimed that the only folks who were interested in the book were cartridge collectors. Perhaps there will be more information given if anyone ever does a book on the FN Minimi.

DTIC doesn’t show much on the topic in their public section, and doesn’t have anything available for download.

The third edition of HWS will hopefully add to what is known regarding the ammunition.


Here’s a link to a thread from a while back. Shows many of the different cases. Unfortunately it’s a couple of years old and some of the photos are gone.

I guess it was decided that the 5.56x45 was a good enough cartridge after all since the current M249 uses it and gives every indication of being around for a while.

I’m gone for a week so you guys have fun with this.

iaaforum.org/forum2/viewtopic.ph … hlight=6mm


Here are a few:


  1. .25 Ballistic Test, W C C 5 8 (ballistic test for SAW program using left-over .25 Winchester cases)
  2. 6x44 pre-SAW, F A 7 1 (no primer)
  3. 6x45 Brunswick, WCC 74 556 (blind primer pocket)
  4. 6x45 SAW inert, brass case, F A 7 2 (blackened primer)
  5. 6x45 SAW ball, brass case, F A 7 2
  6. 6x45 SAW tracer, brass case, F A 7 2
  7. 6x45 SAW inert, steel case, F A 7 3 (blackened struck primer)
  8. 6x45 SAW ball, steel case, F A 7 2
  9. 6x45 SAW ball, steel case, F A 7 3
  10. 6x45 SAW tracer, steel case, F A 7 3
  11. 6x45 SAW proof, chromed steel case, F A 7 3
  12. 6x45 SAW ball, plain steel case, F A 7 3
  13. 6x45 SAW ball, teflon-coated steel case, F A 7 3
  14. 6x45 SAW ball, experimental phenolic varnish, F A 7 3
  15. 6x45 SAW ball, cook-off test, normal powder charge, inert black primer, F A 7 3
  16. 6x49 SAW inert, F A 7 2 (blackened primer)
  17. 6x49 SAW ball, no headstamp

Sorry for the marginal photo quality. If there is interest I can take better photos of individual rounds.

As I understand it, the 6x50 length was developed for the aluminium case, because to avoid the risk of “burn through” (aluminium being potentially inflammable) the case interior was lined with a fireproof material. This reduced the case capacity so the case was lengthened to compensate, in order to match the ballistics of the 6x45.


Great display of related items. It would appear based on your item #1 that the late '50’s experiments were not forgotton when the SAW project started.


Thanks for the input. The excellent thread Ray linked above shows a 6x45 aluminum case that must have been tried and perhaps failed due to burn through or suffered from lack of performance if the liner was used. All very interesting stuff. P.S. My thanks to you for your fantastic web site and the superior quality of your published works.


As I posted in the earlier discussion, the lacquered steel cased ball and tracer were pretty common for a while at gun shows in the 1980’s. I remember one guy had hundreds of these. How did such a quantity of this ammo make it into civilian hands? Was the left over ammo from the SAW trials surplussed?

Also, any pics of boxes, labels or ammo cans for the 6mm SAW out there?


In 1969 the British carried out research into the ideal calibre (again!) and came to the conclusion that 6.25mm met all the criteria. This resulted in a report in November 1969 entitled “Future Small Arms, an intermediate calibre solution.”

Although never adopted, there has long been a suspicion in the UK that this work inspired the US SAW project.

Ballistic trials were held using newly made 7mm (,280/30) cases necked down to 6.25mm and headstamped “RG 69 6.25 x 43”. Cases were also dated 70 and 71.

This shows the comparison between the cases.

A variety of bullet forms were tried, mostly of a nominal weight of 100 grns at 2680 fps.

In addition to the various ball rounds, dummy and proof rounds were loaded and the trial weapons were an EM2 and L-E No.4 rechambered to 6.25mm.

These are three of the bullets tried, all are GMCS jacketed but although of different lengths all weigh 102 grns ± 0.5 grns.

Now for the connection. The actual cartridge was never made, but brass mock-ups were manufactured of the proposed form. Although I do not have one, I have seen an example.

All I have is a very poor third generation photocopy from the research paper, but it can clearly be seen that the general form closely resembles the SAW of a year or so later.

That’s the conspiracy theory for today,


Sorry, double post.


yes the 6x45 SAW was made in aluminum. Very rare only aware of 2 or perhaps 3.
For those of you who like variations look for dished heads in the steel cased rounds.
Earliest 6x45mm date I have is F A 6 7, a plain (in the white) steel unprimed case