7mm Compromise, T65/7mm


During 1951 to 1953 the BBC (Britian/Belgium/Canada) Committee was formed in one last attempt to develop a new 7mm round acceptable to NATO. One of the cartridges they produced was the 7mm Compromise, also know as the T 65/7 mm. It was comprised of the US FAT1E3 case necked down to take a 7mm bullet. Versions of the cartridge were made in the three BBC countries as well as in the US. Below are examples, along with a .280/30 and a FAT104E1 for comparison. I would like to hear from collectors who have others, made on the US case, FAT1E3 or otherwise, and any provenance of same.

Left to right:

.280/30 hs RG 50 280/30, Brit Type B bullet
Compromise, hs DA^ 52, Canadian
Compromise, hs FA 51, Brit Type B bullet, case neck shortened to allow crimping in cannelure
Compromise, hs FA 52, Belgian bullet
FAT104E2, hs FA 51



British 7mm Ammunition trials

There is also a 7 x 49 mm canadian experimental based on a .30 FAT1 case (7.62 x 49 mm) headstamped F A 48. Bullet is british Type “C” with pink tip.

British made 7 x 51 mm Compromise rounds are headstamped RG 52 7M/M and RG 53.

Belgian production of same cartridge is headstamped F N 52.

Ray, do you have any document calling this cartridge a “Compromise”? I’ve never heard of such a designation for this round.



Thanks for that information.

I’m familiar with the Brit and Belgian cartridges but not the Canadian. Do you have a photo of it? Or know where I can get a photo? And do you know what the provenance is? FAT1 cases would have been more commonly headstamped FA 48 *. Does it have the "star’ in the headstamp?

7mm Compromise or T 65/7 MM are the terms used by Brit collectors to describe the cartridge. Lacking any other official designation, it’s what I use. The official design is D6/L/1125.

Thanks again



Ray, I believe that Paul Smith probably have an example of this round. I’m sure that correct headstamp is F A 48.

What I meant to ask you was the use of the name “Compromise” for the US 7 x 49 mm cartridge and not the british/canadian/belgian rounds.



As I said, lacking any other designation, official or otherwise, I used the term so as not to confuse the issue further. Note that the 49mm case that I showed was only shortened to accomodate the cannelure on the Brit bullet. The Belgian bullet had no cannelure so it was not necessary to shorten the case. If these rounds were loaded by Springfield or Frankford for a one-time test of the design, there’d probably be no need for any sort of drawing or official designation.

I’ll concede that I have nothing to confirm an official designation for the shortened case cartridges. The primary reason for my IP was to try and sort everything out. If you, or anyone, has anything in the way of drawings or documents that will clarify things, I’d be really appreciative of seeing them.

I should have stayed with my first interest - the Cal .30 LR cartridges. ;) Carolyn’s post about the .280/30 cartridges caused me to take another look at my “Compromise” cartridges. I should have known that things can only go downhill from there.



I have the same ‘F A 51’ as yourself but I’ve listed mine as ‘7mm FA-T1E3’ if only for the reason that I think it’s a logical designation until a box label turns up!
Could I query the headstamp on your Belgian cartridge (4th in the row). Is it really ‘F A 52’ rather than ‘F N 52’?



That is not a Belgian cartridge with the F A 52 headstamp. I have the same round. It is an Frankford Arsenal case loaded with the Belgian S12 bullet for trials in the U.S.

Fede/Ray - I will check my documentation to see if I can find an official reference to the name “Compromise”.



I have had a quick search of my drawings and found this one which shows that the name “7mm Compromise” was in official usage. Unfortunately it is undated but it is certainly contemporary to the development of the round. It is interesting that the name shown is “7mm H.V. Compromise”, presumably because it was a follow on from the earlier 7x49mm H.V. round. Note also the Boxer primer.

At about that time the 280/30 was being referred to as the “7mm L.V.” in official memos etc.

Sorry about the quality but the original has faded over time.




Interesting drawing. Thank you for posting that. It is curious that despite the description below it, the dimensions seem to be for a regular 7.62x51mm case. Note the case mouth diameter is shown as .3078"/.3068" dia. which would be a bit loose for a 7mm projectile. Perhaps I’m missing something?



Dave - You are right. All dimensions are the same as on FA drawing FB25449 which is the FAT1E3 case.

Jim - I assume that your “7mm FA-T1E3” is also shortened to 49mm +/-? There are several of these cartridges in collections, with different Brit bullets. Does yours also have the Type B?

The full length case with the Belgian bullet is fairly common.

All - I’m still trying to track down the one on the FAT1 case that Fede mentioned. I would almost bet that it is on the FAT1E1 case, assuming it exists. I’ve yet to see a T1 case without the star or a T1E1 with the star although they are reported to exist.

Anyone else have one of Canadian 7mm Compromise cartridges? I’ve only the one. The bullet appears to be GM Steel core, but i don’t know the weight.



I never even noticed the diameter of the neck! I wonder why it was titled “7mm Compromise” but drawn with a .30 calibre neck?

Ray - the only Canadian Compromise I have is also a mild steel cored bullet. I do have a Canadian 7mm 2nd Optimum but that is only an empty primed case.



Tony - did you get my email with the enhanced version of your drawing attached??
I had two email addresses for you and not sure the one I sent it to is current or not.



I have some little extra information about US variations:

  • 7 x 49 mm cartridges were loaded at Springfield Armory.

  • 7 x 51 mm cartridges also exist with F A 53 headstamp. I have an old cartridge collector trade list in which was one these rounds is described as a FA variation of the “.27 Homologous Cartridge for Light Rifle”. While wrong, these are apparently similar (case lenght, neck diameter and bullet diameter are different).


I have two 7x51s, DAC 52 and RG 53,
the RG has a slightly unusual headstamp in that is looks like the bunter was originally a 3 section
headstamp at 12, 4 and 8 oclock but now the RG is at 12 and the 53 is at 4



The US 7mm cartridges were loaded at both FA and SA.

One with an FA 53 headstamp would be a lot less common than any others. FA 53 cases, in general, are very scarce, more so if loaded with a 7mm bullet.

You’re correct that the Cal .27 for LR cartridge is not related to the 7mm in any way, as far as I know. They were loaded by Western as part of Project SALVO. Only the neck and bullet diameter are different.




  Do you mean that 7 x 49 mm were also loaded at FA or only 7 x 51 mm cartridges?

  Case lenght of .27 cartridges is a little bit longer:

  .27: 51,65 - 51,80 mm (2.033 - 2.039")
  7 mm: 51,00 - 51,31 mm (2.007 - 2.020")



I’ll be posting some information soon that will give a lot more insight into the US loaded 7mm cartridges. But yes, both were loaded by both FA and SA.

The SALVO cartridges all used the LR case so they are nominally the same length. There are always slight differences between cartridges, especially those made and loaded by different manufacturers. Necking a case down to a smaller caliber will slightly lengthen the case so you will find that the Cal .18 for LR case is usually longer than the Cal .22, and so forth. Plus, you have a built in manufacturing tolerance of .015" to start with.

And to throw in a little of my traditional nit-picking, US case length is not expressed in mm, but in inches. I’m often guilty of using mm but it’s not really correct.



Ray, thanks. It would be great to have that information.

I have edited my previous post to include measurements in inches. It was also very interesting to learn what nitpicking really means!


John - Yes thanks, I did receive the enganced drawing but did not get round to responding last night. I actually posted a reply on here this morning, but it is another one that disappeared into the wild blue ether!

Craig - Your RG headstamp is normal for the 7mm 2nd Optimum and early 7.62mm rounds. It should be read with the “RG” at ten o’clock and the “53” at two. You will find that headstamp on all loads of the 7mm 2nd Optimum and on 7.62mm ball, tracer and AP for 1953 and 1954.



The following information came from a very reliable source. I’m confident that it is accurate.

The first .280 loading by Frankford Arsenal was during January, 1950 when the Arsenal loaded a small quantity of .280 cartridges, with FA bullets, in FAT1 cases headstamped FA * 48. FA was very likely aware of the UK .280 developments and decided to obtain some preliminary ballistic data. Test firings of this round at FA were in a Mann Test barrel.

The next loading was in early 1951 when FA loaded a series of test rounds using UK bullets in FAT1E1 cases headstamped FA 48 and FA 50. (The cartridge that Fede attributed to Paul Smith may be one of these, although I’m still waiting to hear from Paul with details of his.) Reportedly, Springfield Armory also hand loaded FAT1E1 cases using components provided by FA for tests in one or more “T” series rifles which had been chambered for this cartridge. As far as I know, all FA tests were conducted in test barrels rather than rifles.

(As a side note, FAT1E1 cases, headstamped FA 50, were also loaded with T104 Ball bullets and tested by SA in one or more “T” rifles. This is a very uncommon cartridge, not usually found in collections. I have only seen one, which I own. I do not know who loaded it.)

Finally, in late 1951 - early 1952 FA loaded test quantities using the FAT1E3 case headstamped FA 51 and FA 52 using bullets provided by the UK. Firings of this loading at FA and Edgewood Arsenal were in test barrels. These are most likely the cartridges that have been shown on this thread. It is also possible (and I think very likely) that SA chambered a LR for this round, but this has not been confirmed.

So it would appear that FA and SA were both testing .280 cartridges as early as were the British and Belgians. I think there is a common misperception that the US dismissed the .280 as a possible NATO cartridge, out of hand, when the opposite is true. They did consider it enough to do actual testing of different cartridges over a 3 or 4 year period but, as we know, opted for the .30 caliber, for various military, and political, reasons. But, that’s my own opinion only so take it for what it is worth.