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.

 

 

 

 

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 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

 

• Top Row Both sides of an automatic gas-check Mk II for the 8 inch 70 cwt howitzer. The face in the left image is exposed to the powder gas, while the face in the right image lies against the projectile. The 24 projections in the left image are indicative of the 70cwt howitzer. The second and third lines of text in the left image appear to be "70 CWT" and "II" respectively. The "II" indicates Mark II. The 8 inch 70cwt howitzer did have Mark II gas-checks.

• Bottom Left Automatic gas-check for RML 6.6 inch gun or howitzer.The face shown is exposed to the powder gas. The E.O.C. marking indicates the manufacturer, while the 20 projections are indicative of the 6.6 inch gun and howitzer.

• Bottom Centre Attached gas-check Mark II for RML 9 inch studded ammunition. The face shown is exposed to the powder gas. The hole is indicative of an attached gas-check for studded ammunition. The hole surrounds a circular collar on the attaching plug, permitting the gas-check to rotate relative to the projectile on loading, aligning the projections on the gas-check with the studs on the projectile. The flat disc around the hole is where the head of the attaching plug lies. The wavy nature of the gas-check disc is clearly visible. The six wide projections around the edges are indicative of a 9 inch gun with Woolwich rifling.

• Bottom Right Automatic gas-check for RML 16 inch studless ammunition. The face shown is exposed to the powder gas. The 33 small projections around the edges are indicative of the 16 inch gun.

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

 

More Details https://www.wikiwand.com/en/Gas-checks_in_British_RML_heavy_guns