The British Empire once fielded the greatest military force to sail the seas and conquer the world. With that great military success, some influential small arms cycled through British service during the 20th century, almost all chambered for the .303 British cartridge. 

Outdated in the modern world, the .303 British round has been relegated to the annals of history, but its rich history is still worth exploring. 

Table of Contents

Introduction of the .303
20th Century Service
Pitfalls and Retirement of the .303
The .303 Today


During the late 19th century, firearms technology drastically changed to fit a more modern battlefield. From breech loaders to bolt actions and black powder to smokeless, many advancements were adopted. The British .303 cartridge has the distinct honor of being part of pretty much all the major changes for the Empire around this time. 

The .303 British round played a major role in Great Britain's success in 20th-century conflicts. (Photo: Paul Peterson/

Many of Great Britain’s colonies and provinces across the globe were involved in long-standing conflicts. Before the adoption of the .303 British cartridge, the British military relied on the falling-block, single-shot Martini-Henry rifle, which fired a massive .577/450 bullet propelled by black powder. 

While a nearly .60-caliber round sounds devastating, remember that black powder was not the most effective propellant of the time. The 480-grain projectile topped out at around 1,300 FPS, limiting the range and accuracy. During several conflicts in Africa, the Martini-Henry was pitted against Mauser bolt-action rifles, many with magazines fed by Mauser stripper clips, which gave the enemy a great speed and distance advantage. 

Related: My First Gun – Classic Surplus Mauser

Around the same time, smokeless powder was beginning to become the military standard, following the French adoption of the 1886 Lebel in 8mm Lebel smokeless. Smokeless powder nearly doubled the velocity and range of the standard infantry rifle for a major advantage on the battlefield. 


Introduction of the .303

Taking all these changes into account, the British began working on a new rifle and cartridge to keep up with modern military trends. In 1888, a British Canadian small arms inventor named James Paris Lee introduced the .303 British cartridge. 

.303 British ammunition
While designer James Paris Lee intended the .303 British round for use with smokeless powder, it took a few years to get there, starting out with black powder. (Photo: Paul Peterson/

This 7.7mm bullet sat in a 56mm rimmed cartridge. Lee had always intended that the round be set for smokeless powder; however, it would spend the first few years as a black powder cartridge. 

Alongside the introduction of a new cartridge, the Martini-Henry was replaced with the Lee-Medford rifle, a bolt-action, magazine-fed firearm that increased the speed of fire for the soldier. Unfortunately, the Lee-Medford rifle was still only designed for black powder and saw issues with accuracy past a few hundred yards. 

.303 British cartridge breakdown
The .303 British uses a 7.7mm bullet in a 56mm rimmed casing. (Photo: Paul Peterson/

Shortly after the rifle was introduced, it was replaced with the Lee-Enfield, and the .303 British cartridge was finally paired with the smokeless powder as the designer intended. 


20th Century Service

The newly adopted .303 British cartridge would come into a great deal of fame during the 20th century. The new smokeless powder design propelled a 174-grain bullet at excess of 2,500 fps, increasing the effective firing range to around 600 yards. With almost double the range, the round would find itself in some of the most iconic firearms designs of the British Empire, enduring both world wars.  

Enfield No. 4 Mk 1 bolt action rifle
The Enfield No. 4 Mk 1 in .303 British fought off many Germans during World War II. (Photo: Paul Peterson/

The Short Magazine Lee-Enfield, or SMLE, saw several iterations and designs that served through the British Empire aup until the rifle’s retirement from the Canadian Armed Forces in 2018.

Related Review: England's ‘Last-Ditch’ Rifle – The Enfield No. 4 Mk 1

As one of the only bolt-action rifles of the time to feature a 10-round magazine, the SMLE was known for its speed and accuracy, and a soldier could fire for longer periods between reloading than his battlefield counterparts. In fact, the famous British “Mad Minute” was born from the .303 cartridge and the Lee-Enfield. The Mad Minute was a British rifle exercise wherein an infantryman was required to hit a 12-inch target 15 times in a single minute, at 300 yards. The soldier would start with five rounds in the magazine and reload five-round charger clips throughout the exercise.

Enfield 10-round magazine
The Enfield used a 10-round detachable magazine. (Photo: Paul Peterson/

The Lee-Enfield was the main service rifle for the British throughout WWI and continued to serve through WWII. The .303 British cartridge became the main service cartridge for the British Empire, finding use in the iconic pan-fed Lewis gun, Vickers Machine guns, Browning 1919 aircraft machine guns, and the British Bren gun. Ultimately, the .303 cartridge saw every British battlefield for over 70 years. 

Bren Mark II rifle
The .303 British cartridge was used in the firearms such as the British Bren gun shown here, the iconic pan fed Lewis gun, Vickers Machine guns, and Browning 1919 aircraft machine guns. (Photo: Samantha Mursan/


Pitfalls and Retirement of the .303

While the .303 has bolstered an impressive resume, it was unfortunately a dated cartridge. There is a reason that pretty much every rimmed cartridge has been retired from mainline service. A major disadvantage to the cartridge is “rim lock,” when two rimmed cartridges stacked in a magazine stick together.

rim lock with .303 ammo
"Rim lock" occurs when the rim of the top round is not properly indexed with the rim of the round underneath it, so the bottom rim prevents the action from cycling by holding the top round in place.(Photo: Samantha Mursan/

If the rim of the top round is indexed behind the rim of the round below it, the two lips lock against each other, preventing the action from cycling. Rim lock malfunctions were unfortunately all too common, and soldiers paid dearly in combat. With most nations adopting rimless cartridges around the same time that the .303 British round entered service, it was almost inevitable that the .303 was dated. 

After World War II, the Allied nations started to consider universal rifle cartridges for battlefield use. After a strenuous debate over which round to adopt, the United States led the charge in the 1950s with the adoption of the 7.62 NATO round. 

7.62 NATO ammo
The .303 started to phase out with the introduction of 7.62x51mm NATO in the 1950s. (Photo: U.S. Navy)

The British soon followed suit, thus ending the reign of the .303 cartridge in British military service. While many commonwealth nations followed the Brits, .303 continued to serve in minor roles across small nations throughout the late 20th century. 


The .303 Today

The .303-chambered Lee-Enfield still finds itself on the battlefield well over 120 years after its adoption. The rifle was often seen in Afghanistan with assorted generations of locals, as the robust design and full-powered .303 cartridge were ideal for use at a distance in the mountains. 

.303 British ammunition
A box of American-made WWII-vintage Winchester .303 British ammo. (Photo: Paul Peterson/

However, the saga of the .303 British round has come to an end in the modern age. Relegated to the same level as the 8mm Mannlicher, 7.7 Arisaka, and 6.5 Carcano, .303 is now a surplus cartridge only produced in limited runs marketed to collectors. 

While millions of rounds of military surplus .303 exist in places like India, Africa, and parts of Asia, the surplus is quickly drying up as only a handful of companies still produce the cartridge.

.303 British ammunition
If you get a chance to shoot .303 British, don't pass on the chance to experience a round with a resume that includes two world wars. (Photo: Paul Peterson/

It’s easy to forget about rounds like the .303 British with modern intermediate cartridges dominating the market, but it would be a sin to forget the legacy and pedigree of a round that served in the largest conflicts the world has ever seen. While it may not be your next hunting cartridge, it is worth finding an old Enfield, grabbing some surplus or PPU ammo, and taking a step back in time on the range.

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