Cartridges : Projectiles : Gas Checks : Fuzes & Tubes

Gas Checks


A gas check is flat plate of metal used to impart spin to a projectile in a rifled gun and to seal the bore. It is placed behind the projectile on loading the gun and falls away when the projectile leaves the muzzle. The idea emanated from the Elswick firm and was a means for overcoming erosion caused by windage. The first gas checks were a cup of papier-mâché. These were replaced in 1878 by ones constructed of copper with 3% zinc so they would not break up in flight. A later adaptation was to fix the gas check to the projectile. Because the gas check made the shell rotate, studs were no longer required. This was the precursor of the copper driving band on modern B.L. shells. The earlier gas checks were smooth and the action of firing expanded them into the grooves of the rifling. When slow burning powders were introduced this occurred more gradually and gas checks with ribs to fit the grooves were produced. They were used with all RML studless projectiles except case shot, and with studded common and Palliser for 9-inch and upwards; the 40pr common and shrapnel and 12.5inch studded also fired with gas checks.


The first pattern Mark I were made with a smooth rim and were nutted on to the base. Because they did not expand into the grooves with slower P. powder the Mark II was introduced. This had projections on the rim and was also nutted onto the base but was allowed to revolve so that the projections might not interfere with the loading. It was discovered that the rotation to the shell might be imparted by the gas check and thus obviate the need for studs. This led to the automatic gas check for studless shells. It was loaded separately and was firmly attached to the shell on discharge. It took the rifling of the gun and thus imparted rotation to the shell.


8inch RML Howitzer Gas Check 12-5inch RML Gas Check 10inch shell with Gas Check 11inch shell with Gas Check 16inch shell with Gas Check




gas check
gas check

8-inch RML Howitzer (front)
Found South of Fort Bovisand, Plymouth

8-inch  RML Howitzer (back)
Photos : Paul Frear

The gas check for the 8-inch Howitzer was suitable for common and shrapnel shells, the curved portion of the base of the shell being cast with radial grooves into which the inner surface of the gas check is compressed by the pressure on firing; the gas check is also at the same time firmly attached to the base of the shell by being compressed into the groove or neck round the locking rim at the rear end of the shell. It is made with projections round the circumference corresponding with the rifling grooves of the howitzer.

6.6-inch gas check

9inch R.M.L. gas check 16inch R.M.L. gas check

6.6-inch RML Howitzer

9inch R.M.L.

16inch R.M.L.


Description of the above gas checks kindly supplied by Mike McLean.

Detailed information on Gas Checks can be seen in the Wikipedia article here:

Gas-checks in British RML heavy guns


The National Army Museum have two gas checks for a 6.3in RML Howitzer in their collection. They can be viewed here:
National Army Museum: Gas Checks


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