7.62mm NATO Experimental
Whilst it is not the purpose of this site to cover every type of experimental ammunition in great detail, it is essential to cover the more important types as they are part of the overall story of British service ammunition.
Experimental Ball
During the development of the 7.62mm ball round and subsequently there has been a considerable number of experimental ball round designs. The more important trials are shown below.
Initially, problems of separated cases in Bren guns and poor accuracy in part worn hot rifle barrels occurred. In an attempt to improve accuracy bullets were produced with diameters of .3105, .3125 and .3145 inch. It is known that the latter type had a headstamp of "RG 54 A1" and was identified by two red paint blobs on the head.
The Bren gun problem was eventually solved by the introduction of the stronger L2A2 case, but prior to that it was thought that case taper played a part. Cases were produced with a taper of .016 inches per inch and were headstamped "RG 56 .016".
Although no demand existed in the UK, steel cored bullets were also produced based on the American M59 bullet during 1953/54.
In September 1954 a bullet was produced to design D6/L/1433/G/88. This had a short steel base plug behind the lead/antimony main core designed to give better "set-up" when fired. This was known as the "ST" or "three piece" bullet.
In the same period several lead cored flat based bullets were designed, weighing 9.72g (150 grains) and 11.0g (170 grains).These were:
D6/L/1255/G/88. Flat based weighing 11.0g
D6/L/1266/G/88. Flat based with GMCS envelope and paper tip filler weighing 9.72g
Both of the above were loaded into cases headstamped "RG 54 A1" with two pale blue paint blobs on the head. for identification.
D6/L/1293/G/88. Three variations of the above two designs with different ogives and weights of 9.72g and 11.0g
Left to right:
170 grn Flat based ball bullet D6/L/1255/G/88
"RG 54 7.62A1" case for above
Unknown red tipped exp. Ball, RG 55 7.62A1
Ballistic standard, RG 55 7.62L2A2
ICI Kynoch also conducted experiments with steel cases in 1955. The cases were lacquered dark grey green in the manner of German 7.92mm rounds. The headstamp was "K55 7.62 A2".
This was part of a wider trial of steel cases including 9mm, but no further work took place as far as is known.
Right: Kynoch steel case 7.62mm.
Experimental Tracer
A vast amount of experimentation took place with 7.62mm tracer ammunition, mainly to improve ballistic matching with the ball round, but also to develop a longer range tracer. The experiments took place from 1957 until the end of the 1960s.
In addition to military trials at the request of the MoD, Kynoch carried out a large number of internal trials. The result is a very confusing range of experimental rounds with coloured tips and/or head stripes which are difficult to relate to particular trials. It is impossible to describe every variation here, but the more important ones relating to British service trials are shown below.
Degraded Ogive Tracer
As the tracer composition burned, so the bullets became lighter such that by 1000 yards the tracer bullet was a poor match with ball. One solution was to reduce the muzzle velocity of tracer, but this gave unacceptable energy for operating weapons and the port pressure failed to meet the NATO standard.
An alternative was to reduce the ballistic coefficient of the bullet by using a degraded ogive which had the advantage of maintaining port pressure whilst giving a better match with ball. Studies suggested a bullet ogive of 4 CRH (Calibre Radius Head) fired at a muzzle velocity about 12 metres per second less than ball would give the best match whilst one of 5 CRH would be less advantageous.
One disadvantage of this approach was that the 4 CRH bullet required ball powder to be used whilst the 5 CRH bullet could be used with either ball or NNN powder. Both types were extensively tested.
The first degraded ogive bullet originated in 1957 to design S1/14041/GF/1382 and had a 4 CRH bullet with a red tip. It was given the nomenclature of XL3E1.
Left; XL3E1 tracer manufactured by Radway Green in 1957.
The main trials took place in the early 1960s commencing in 1961.
Two designs of bullet were produced, one with a 4 CRH ogive and the other with a 5 CRH. They were:
4 CRH DD/E/20863/GF/383, weighing 8.9g (137 grains). Dark blue bullet tip.
5 CRH DD/E/20864/GF/383, weighing 8.9g (137 grains). Dark green bullet tip.
In addition to these there were a number of bullets with conventional ogives tested as well as a yellow tipped round with about a 3 CRH ogive.
Above: 1961 trial rounds.
These trials continued for several years. Early rounds were loaded on ball cases and were headstamped "K61 L2A2 (+)" or "K61 L5A1" but some from the following year used tracer cases and were headstamped "K62 L5A3".
Obviously loadings varied for the trial but examples are:
1962: 4 CRH bullet loaded with 0.55g (8.5 grains) of modified SR390 tracer composition with 0.113g (1.75 grains) of priming composition SR867 (called DI34 by ICI Kynoch). Propellant charge was 2.94g (45.4 grains) 2,746 fps).of ball powder to give a muzzle velocity of 837 metres per second (2,746 fps).
1962: 5 CRH bullet loaded with 0.55g (8.5 grains) of modified SR390 tracer composition with 0.113g (1.75 grains) of priming composition SR867 (called DI34 by ICI Kynoch). Propellant charge was 2.66g (41.0 grains) 2,746 fps).of NNN powder to give a muzzle velocity of 827 metres per second (2,713 fps).
1963: 4CRH loaded with 2.91g (44.9 grains) of ball powder BS25422. No details of bullet or velocity are known. From the handwritten comment on the label shown below it seems 5,000 rounds were loaded of this variant.
Example labels for the 4 CRH and 5 CRH bullet trials.
Other designs from this period were:
DD/E/24574/GF/383 - Weight 9.4g (145 grains) 4 CRH.
DD/E/22377/GF/383 - Weight 8.9g (137 grains) 4 CRH.
DD/E/22376/GF/383 - Weight 9.4g (145 grains) 4 CRH. This became the XL10E1.
DD/E/24573/GF/383 - Weight 9.4g (145 grains) 4 CRH. This became the XL10E2.
Work continued in 1964 on a series of long range tracers to give a trace of 1300 metres. The starting point was the XL10E1 tracer from the previous trials but fitted with a modified tracer composition to give a longer burn. Special high density metal tips of "Mallory" and other metals were fitted also.
Further trials of long range tracers took place in 1968 including:
- an L5A3 bullet with no canister identified by a blue stripe on the case head.
- an L5A3 bullet with SR607 composition and NNN propellant. this became the XL5E5 round.
- an XL10E2 bullet identified by a red stripe on the case head.
- an XL10E2 bullet to design DD/E/24551/Sk/383 with a 7 degree boat tail identified by a black case head stripe.
- an XL10E2 bullet with a 10 degree boat tail.
- an FN experimental tracer.
- another FN experimental tracer.
Example rounds from the 1968 trials.
Further trials in 1968 covered the "20 series" of experimental bullets. These were:
Type 20/1 to design DD/E/24992/GF/383 with 9 degree boat tail, weight 8.9g (137 grains), no canister.
Type 20/2 to design DD/E/24995/GF/383 with flat base, weight 8.3g (128 grains), no canister.
Type 20/3 to design DD/E/24998/GF/383 with 7 degree boat tail, weight 8.3g (128 grains), no canister.
Type 20/4 to design DD/E/25135/GF/383 with flat base, weight 8.7g (134 grains), 15mm canister.
All were identified by red over mauve bullet tips and were loaded with two different types of tracer composition, SR607 and H8.
To identify the different tracer compositions the markings were:
Type 20/1 with SR607 - 1 blue stripe Type 20/1 with H8 - 2 blue stripes
Type 20/2 with SR607 - 1 green stripe Type 20/2 with H8 - 2 green stripes
Type 20/3 with SR607 - 1 purple stripe Type 20/3 with H8 - 2 purple stripes
Type 20/4 with SR607 - 1 red stripe Type 20/4 with H8 - 2 red stripes
In the event, none of these experimental tracers were ever approved for service
Incendiary Tracer
A requirement arose in 1957 for an 7.62mm observation round to be used for ranging with the 120mm Battalion Anti-Tank (BAT) recoilless weapons. Until then this role had been filled by a Bren LMG firing .303 inch G8 tracer.
It was stated that to achieve the smoke and flash required no internal striker was to be used. Two designs ensued.
ICI Kynoch produced a bullet to design S1/13377/GF/1390 (ICI Ref. APS 68) which was broadly similar to the L5A3 tracer bullet but with a charge of 0.37g (5.7 grains) of SR 365 incendiary composition in the nose. The tracer canister contained 0.68g (9.0 grains) of composition and the whole bullet weighed 8.4g (130 grains). It was a dark ignition tracer to 100 metres and bright to 1000 metres. Muzzle velocity was 677 metres per second (2221 fps).
It was manufactured by both Kynoch and Radway Green, loaded into cases headstamped "K57 7.62 L2A2" by Kynoch and "RG 59 L2A2 (+)" by Radway Green. It was identified by a red over blue bullet tip.
An alternative design to S1/13970/GF/1382 was manufactured by ICI Kynoch in cases headstamped "K58 L2A2 (+)" (also 1959) and had a blue base stripe
The Radway Green design to S1/13970/- had a 4 CRH bullet and weighed 8.75g (135 grains). The tracer element weighed 1.05g (16.2 grains) and in front of this was a lead disc forward of which was 0.27g (4.17 grains) of SR365 incendiary composition. It traced dark to 200 metres and bright to 1000 metres. The specification called for a red bullet tip but some were left uncoloured.
Right: RG incendiary Tracer.
Bulleted blank
At the beginning of the development of 7.62mm ammunition consideration was given to a wood bulleted blank.
The first such round was made in 1955 to design D6/L/1382/42 loaded with 2.7g (41.7 grains) of Nitrocellulose. These proved unsatisfactory and gave poor extraction and ejection.
Further unsuccessful trials were held in 1956 with both red and blue coloured wood bullets but whilst these functioned well with a blank firing attachment there was excessive blast and unburnt propellant.
The final trials appear to have been in 1959-61 with both Kynoch and Radway Green types noted. The Kynoch version was headstamped "K59 L2A2 (+)" and the RG type "RG 62 L2A2 (+)".
Short Range (Internal Security)
In 1969 work was carried out to develop a short range round for internal security work in Northern Ireland to replace normal ball ammunition issued to troops. It is assumed that these rounds were still considered too lethal and so were not issued, less lethal "rubber bullets2 being retained instead.
Several different short light weight bullet types were tested but the final form used a 7.65mm pistol bullet weighing 5.02g (77 grains). It was covered by design QV46GF and propellant was 0.28g (4.3 grains) of chopped nitrocellulose. The rounds were headstamped "RG 69 L2A2 (+)" and usually had a violet tip for identification.
Short range (SPARTEN/ROTA)
A requirement existed in the 1980s for short to medium range ammunition to maximise use of existing ranges, some with restricted danger areas. It was envisaged that this would use frangible bullets and cover the three main infantry calibres of 7.62mm, 5,56mm and 9mm.
The development was originally called SPARTEN (Special Practice Ammunition for Realistic Training, ENfield) but was later changed to ROTA (Royal Ordnance Training Ammunition).
SPARTEN ammunition was designed to be fired from standard servcie weapons without modification and utilised normal brass cartridge case. Two types were envisaged, "Midi" Sparten was intended to ballistically match L2A2 Ball to 300 metres whilst "Maxi" Sparten was matched to 600 metres.
A wide range of resin and powdered metal bullets were tested, some to normal profile and some blunt nosed. Tracers were also trialled.
Above: Example 7.62mm Sparten bullets.
Once the 5.56mm L85 rifle replaced the L1A1 the requirement for the "Midi" Sparten round disappeared but work on the "Maxi" Sparten continued for a while for use with 7.62mm machine guns. In the end the round was not adopted.