The name "Jungle Carbine" was never an official designation for the No. 5 Mk I Rifle. It was nicknamed the "Jungle Carbine" by British troops during World War II, the Malayan Emergency and possibly the Korean War.
This rifle was a shortened and lightened version of the venerable Lee Enfield, the workhorse of the British Empire.
The No. 5 Mk I “Jungle Carbine” was about 4 inches shorter and 2 pounds lighter than the earlier British No. 4 Short Magazine Lee Enfield (SMLE) from which the “Jungle Carbine” was derived. In order to help absorb the increased recoil; the rifle had new features like a flash hider and a rubber butt pad. The result is a compact rifle that is accurate and powerful.
The “Wandering Zero” problem with the No. 5 Mk I “Jungle Carbine”. There are claims, and even a conclusion by the British Army, that the “Jungle Carbine” has a problem holding its zero during sustained firing. In other words, the impact of the rounds shift with the same point of aim. Actually this is bunk, pure and simple. The guns shoot well, however the increased recoil and shooter fatigue can easily cause the rounds to shift impact. The No. 5 Mk I “Jungle Carbine” was abandoned because the British military did not want a bolt-action rifle when most other countries were upgrading their arsenals to semi-automatic infantry weapons.
What the British created with the Jungle Carbine was remarkable. The rifle was fast handling and powerful. It was the model on which the “Scout Rifle” concept was built. In fact, most scout rifles are not as good as the Jungle Carbine. I’ve had one in the past but the examples in the photos belong to a British firearms collector I know. One example is a true Jungle Carbine, the other is a converted No 4 rifle. These conversions were made by dealers to sell rifles, they shoot just fine.