4.85x49mm
| 4.85x49mm | ||
|---|---|---|
 | ||
| Type | Rifle | |
| Place of Origin | United Kingdom | |
| Designer | Royal Small Arms Factory | |
| Specifications | ||
| Parent case | 5.56×45mm NATO | |
| Case type | Rimless, bottleneck | |
| Bullet diameter | .197 in (5.0 mm) | |
| Neck diameter | .220 in (5.6 mm) | |
| Shoulder diameter | .353 in (9.0 mm) | |
| Base diameter | .375 in (9.5 mm) | |
| Rim diameter | .376 in (9.6 mm) | |
| Rim thickness | .041 in (1.0 mm) | |
| Case length | 1.925 in (48.9 mm) | |
| Overall length | 2.455 in (62.4 mm) | |
| Primer type | Small rifle | |
| Maximum pressure | 52,000 psi (360 MPa) | |
| Bullet Weight | Velocity | Energy |
| 55gr (4g) FMJ | 3,115 ft/s (949 m/s) | 1,190 ft-lbf (1,610 J) |
| Barrel Length Unknown | ||
The 4.85x49mm was a prototype cartridge developed in the United Kingdom by Royal Small Arms Factory. It was used in the early development of the rifle now known as the SA80. In the trails it was known as the XL60. The 4.85x49 is based on the .223 Remington but uses a 5 mm projectile and has a slightly longer neck. Muzzle velocity comparable to the M193 the cartridge was up against with the 4.85x49 firing a 55gr bullet at 3,115 ft/s (949 m/s) and the M193 firing a 55gr bullet at 3,260 ft/s (993 m/s).
In the 1960s the UK was looking for a replacement for the 7.62x51 NATO cartridge. The replacement had to be lighter weight, but also effective. The original plan was to use the .280 British, but a study conducted in West Germany found the ideal cartridge would have a projectile of 5mm or smaller. The idea was that a very small and lightweight projectile would get to very high speeds. After the study was released the United Kingdom decided to switch to the new 5mm projectile for their new rifle program. Several prototype 5mm cartridges were designed and trailed starting off with the 4.85x44, which was based on the 5x44 starting in 1970. The shape of the projectile was based on the 6.23x43, which was another experimental round the British were working on. The cases of these prototype rounds were reformed from the M193. The reasoning behind calling it a 4.85, when the projectile was actually 5mm was because the decision was made to measure from the rifles lands.
As testing continued it was discovered there were issues with the bullet seating in the case. To fix this the case next was elongated by 5mm which is where the 4.85x49 comes from. During testing and before retooling could take place, the RSAF required ammo for testing the new rifles so the 4.85x44 they had on hand was modified and the next was stretched by 5mm to work in the new rifles.
Trails continued with the round and with the L64/L65 throughout the 1970s. The L64/L65 was officially announced in 1976. The following year trails for a new NATO cartridge went underway and the British submitted the XL1E1 (ball) and XL2E1 (tracer) for the trails. The development and ultimately the end to the 4.85x49 came when NATO adopted the SS109 round developed by FN Herstal to replace the M193 on October 28, 1980. In 1979 the British officially switched over from the 4.85x49 they had developed to the new standardized cartridge NATO had chosen. The 5.56x45.
Variations
There were several versions of the 4.85x49 made over its developmental life span
- XL1E1 - Ball - The most common form of the round and what was used in the NATO trails. It fired a 55gr bullet with a muzzle velocity of 3,115 ft/s with a muzzle energy of 1,210 ft/lbf.
- XL2E1 - Tracer - Besides the XL1E1, the XL2E1 was the second most common version of the round. It was also used in the NATO trails. It was noted for having an orange tip.
- Short Range - A version of the round with a white plastic bullet. Most likely used for training purposes.
- Armour Piercing - While developed along side the 4.85x44 and 4.85x49, the armour piercing versions of the rounds were never made in any significant numbers. The round is noted for having a black band around the tip.
Further Reading
If you would like to learn more about the development of the 4.85x49 or the history of the SA80 then please consider reading the following.
