More early British 7.62mm NATO


#1

Following on from my earlier post of some of the early 7.62mm NATO rounds, I thought I would post a few more.

There was considerable experimentation to find the ideal bullet in 1954/55. Part of the problem was getting the best diameter bullet for good set-up and so a number of different sizes were tried. In the end it was easier to reduce the bore diameter from .300" to .296".

Left hand has a .312" bullet, right has .3145" bullet.

Various bullet types were also trialled, apart from the normal 144 grn. boat tailed, This has a 150 grn flat based bullet.

There were also 170 grn flat base.

A three piece bullet had a lead tip filler, a steel core and a lead base pad and was identified by a red bullet tip, but with a normal headstamp.

To counter problems with extraction, the taper on the long cone of the T65 case of .012" was changed to .018" and ammunition headstamped accordingly.

There was also a small contract for ball let to Greenwood & Batley in 1958, but the rounds failed proof and were never issued.

An early proof round is copper washed with a ball headstamp (left) whhilst another is only identified by a red bullet tip.(right)

The earliest tracers were unheadstamped both by RG and Kynoch. One has a plain head (left) whilst the earliest headstamped RG tracer is 1957 (right)

Finally, there was an attempt in 1957 to produce an incendiary tracer to be used as a spotter round for the Bren gun attached to the 120mm recoiless anti-tank gun. It was not approved for service.

Regards
TonyE


#2

Tony,

Another great set of early 7.62 x 51. Could you please elaborate on the use of bullet diameters by the British that would seem out of sorts with compatability concerns of other NATO members? Rude American that I am, I would have thought that .308" nominal dia. would have been a given parameter for the new round to be accepted. Was there still debate on this subject at that time?

Thanks,
Dave


#3

One of the problems encountered with the first British L2A1 ball round was that of torn cases in the Bren. This was overcome by the introduction of the L2A2 case with a strengthened web.

The second problem was lack of accuracy in worn or hot barrels of the SLR (Belgian FAL or L1A1 in British service). The early rifles were made by FN for Britain and had a bore diameter of .300 ± .0005" and a groove diameter of .308 ±.001. Bullet diameter was .308. This also applied to the GPMG which was the Belgian MAG.

Experiments with increased bullet diameters were tried to get better set-up in worn or hot barrels, diameters being .3105", .3125" and .3145".

It was decided that rather than increase bullet diameter, it was easier when Britain started to make her own rifles to decrease bore diameter to .296".

Regards
TonyE


#4

Tony - Great pictures and info. Some of your postings on the (FN 1954 7.62 x 51" thread are much more relative to this thread you started. I would suggest the administrator move those entries to this thread for continurity, but that would be up to you and him, of course.


#5

Tony,

Thanks for the clarification of the purpose of the over dia. bullets. Was thinking they would make a tight fit in a cool M14!

Dave


#6

John

I am more than happy for the “powers that be” to move my posts on British NATO to wherever they think best… I agree that it is a good idea to keep associated threads together.

Regards
Tony


#7

Tony

A question about the altered tapered cartridge. Your example appears to be headstamped .018. I’ve looked at my example which appears to be either .016 or .018 - the last digit is poorly formed. There is a label on the cartridge stating that it is “.016 taper”. Labbett in his booklet on UK 7.62 cartridges states “that the taper be changed to .0165 inch”. The headstamp drawing shows .016. Was there a .016 and .018 taper?

Dave S


#8

I have always understood it to be .018, and my example looks like .018, but I know what PL says. I will see if I can find anything in the records.

Regards
TonyE


#9

I have just noticed a typo on my earlier post about bullet diameter and bore size. I said bullet diameter was .307", but that was just finger trouble for what it should be, .308".

I have edited the post.

Regards
TonyE


#10

Dave - I have had a dig in my files (which I should have done in the first place) and as always found some info I did not know I had regarding the case taper and the different bullet diameters.

Source is an Armament Research and Development Establishment report dated September 1956.

First the case taper. The report states:

At Ottowa in 1954, U.K. delegation had considered that the taper on the long cone of the cartridge case of .012 inch per inch was too slow and might cause extraction difficulties. However, the U.S. was not prepared to increase the taper without strong evidence of the advantages of so doing. It was also considered that the tapers of .005 inch per inch and .013 inch per inch respectively on the short and long cones of the chamber were too slow for satisfactory functioning in automatic weapons. They were, however, considered acceptable for the proof weapon chamber for use in ballistic firings; but it not been the intention of the U.K. to use them in service weapons, although, Messrs. F.N. did use them in the prototypes of the F.N. rifle. P,3., therefore in their work to make the F.N. rifle more reliable in the desert, and to produce a satisfactory conversion of the .303 inch Bren L.M.G. to 7.62mm calibre, have selected tapers of .013 inch per inch and .015 inch per inch in the hope of preventing undue interference between case and chamber. Some special cases with a taper of .016 inch per inch are also being manufactured for use with an even greater chamber taper. Trials are being carried out by P.3. in which the weapon/ammunition performance is assessed by the length of bursts attained while firing in a simulated and “standardised” sand storm. The recent modifications by P.3., together with their proposal to introduce a chromium plated chamber, seem likely to give satisfactory functioning of the weapons with the current L2A2 ammunition.

The taper was therefore maintained at the original figure.

The report makes it quite clear that the experimantal taper is .016, and that is what is on the headstamp. I had misread mine as .018.

With respect to the various diameter bullets, the report has this to say:

“It was found that the streamlined lead cored bullet gave poor accuracy in a hot F.N. barrel to N.A.T.O. design (i.e. bore .300"±.0005”,groove .308"+.001") after less than 10,000 rounds fired in the standard cycle."

It went on to say that whilst the N.A.T.O. requirement was that accuracy was maintained at the end of 5,000 rounds fired at 125 rounds per minute,the War Office requirement was for the S.F.M.G. to fire 8,250 rounds in one hour using not more than three barrels

Accuracy trials were fired at 200 yards in new (1000 rounds) and worn (7,500 rounds) F.N. rifles with lead cored bullets of various diameters. The results were interesting.

The service bullet (.3085") gave a group 12 x 15" in the new barrel and 50 x 40" in the worn.

.3105" bullet gave 9 x 12" and 11 x 13" respectively and the .3125" bullet gave 9 x 12" and 5 x 8".

It was obvious that a great improvement could be achieved with the larger bullets, and ballistic firing trials showed that by adjusting the charge pressure and velocity could be maintained at the correct levels.

Many more combinations of bullet diameter, leed size and rifling form were tried and in the end it was decided that the same reults could be achieved by keeping to the N.A.T.O. bullet diameter of L .3075", H .3085" but reducing the bore diameter of British barrels to .296". This was supported by a U.S. report from Aberdeen that a .296" bore would be more satisfactory than .30" but this work had not been followed up.

I hope that explains things from the U.K. end!

regards
TonyE


#11

Hi there,

Here is an image of the early proof round, as mentioned by TonyE (in the first thread), marked with a red bullet tip.

all the best,
Joost


#12

Tony
Thanks for the additional information the .016 taper cartridge. Were you able to dig up anything on the AP and API with the RG 53 headstamp?

Dave


#13

The bore gauge we used as Armourers to make sure the L1A1 rifle barrels were straight was dropped down the barrel and it’s size was .297"


#14

Sorry dave, I have not come up with anything so far. However I also have an AP round for the 7mm Compromise with the RG 53 headstamp, so there was a definite interest at that time in developing a suitable AP.

Regards
TonyE


#15

How is the 7mm compromise AP cartridge identified?

Dave S


#16

Hi Dave,

Wasn’t the 7mm AP round marked with a green primer annulus?

I have the headstamp, but this case was used as a blank (or Grenade)…

all the best,
Joost


#17

Yes, the 7mm Comp AP has a green annulus. Both the Comp. and the 2nd Optimum also seem to have used a green annulus for the grenade cartridge.

Regards
TonyE


#18

Here are three early dummy rounds. The headstamp of the first 2 rounds are the same: RG 55 7.62 (with nothing in the 5 o’clock position). Note the neck of the middle round is noticably longer than the other 2.

Sorry for the poor quality of the headstamp scan.

Paul



#19

There is also a variation of these exp. dummies with an unchromed cartridge case and red painted flutes (type D) (see image, 3rd round from the left)

I am still looking for the variation with the white flutes, so if someone has a spare one please let me know…

greetings,

Joost


#20

Are the rounds part of the same program only latter???

Thanks
Steve