18 pdr Gun

18 pdr Gun
18 pdr Gun Mark 1 on Mark 1 Carriage

The 18 pdr Gun was introduced in 1904. More than 10,000 were made of the original model. Work began in 1916 on an improved design but it wasn’t until 1918 that it went into production as the Mark 4 Gun on Mark 3 Carriage. This was a big improvement with a box trail and Asbury breech mechanism. It became the standard field gun in the post-war years. It was improved still further in later years with a split trail carriage and pneumatic tyres. By the end of its life there had been five Marks of Gun and five Marks of Carriage with many sub-Marks in each.

When the 25 pdr Mark 1 was introduced, a number of 18 pdrs were coverted by simply changing the barrel. As the 25 pdr took some time to come to full production, the 18 pdr stayed in service for most of WW2. Eventually, the Mark 4 was made obsolete in August 1940 as the last one was converted to 25 pdr. The rest remained in use until 1944 having been used for training and then anti-invasion defences in 1940-41. They were also used in the Middle and Far East.


Mark 1Original pattern. Wire-wound, screw breech, 1904
Mark 1*Mk 1 repaired by insertion of new ‘A’ Tube and wire. Gun assembled by
hydraulic pressure
Mark 2Gun assembled by hydraulic pressure instead of heating/shrinking 1906
Mark 2*Mk 2 converted for AA mounting in 1915. Converted back in 1920
Mark 3Development model not adopted 1917
Mark 4New design, Asbury breech mechanism 1918
Mark 4AMk 4 repaired by replacement of ‘A’ Tube & wire by auto-frettaged
loose liner 1935
Mark 4BAs Mk 4A but new manufacture 1935
Mark 5As Mk 4 but differences to suit Birch Gun mounting 1926


Mark 1Original, pole trail, hydro-spring recoil, elevation 16º 1904
Mark 1*Mk 1 modified to hydropneumatic recoil system 1916
Mark 1RMk 1 with solid rubber tyres
Mark 1*RMk 1* with solid rubber tyres
Mark 1**Mk 1 * with lengthened cradle
Mark 1CMk 1 with extended cradle
Mark 1DMk 1 with Mk 2 Carriage cradle
18 pdr Gun
18 pdr Mark 2PA
Mark 2Similar to Mk 1 but hydropneumatic recoil system & longer cradle
Mark 2*Mk 1* but with Mk 2 Carriage cradle
Mark 2PA‘Martin Parry’ conversion, pneumatic tyres on steel disc wheels
Mark 2RMk 2 with solid rubber tyres
18 pdr Mark 4P
Mark 3For Mk 4 Gun, box trail, extended cradle, hydropneumatic recoil, elevation 30º
Mark 3TMk 3 modified to approximate Mk 4 standard
Mark 3*As for Mk 3 but elevation 37½º
Mark 4As Mk 3 but new trail & traversing gear. Shock absorbers between axle & trail,
elevation 37½º
Mark 4RMk 4 with solid rubber tyres & elevation 38º 40′
Mark 4PMk 4 with pneumatic tyres & elevation 37½º
Mark 4TRMk 4 but with only 30º elevation
18 pdr Mark 5P
Mark 5Split trail, 50º traverse, 38º 55′ elevation
Mark 5RMk 5 but with solid rubber tyres
Mark 5PMk 5 but with pneumatic tyres, 37½º elevation


Gun Mark 4 on Carriage Mark 5P

Weight of gun & breech mechanism952 lbs
Total length96.96 inches
Length of Bore92.735 inches (28 calibres)
Rifling18 grooves, uniform Right Hand 1/30
Breech mechanismAsbury interrupted screw, precussion fired
Elevation-5º to 37½º
Traverse25º right & left
Recoil systemHydropneumatic, variable, 26 to 48 inches
Weight in action3,507 lbs


Firing standard 18 lb HE Shell

Muzzle velocity1,625 feet per second
Maximum range11,100 yards


Fixed case charges

A huge number of shells & cartridges were approved during the gun’s 40 years service. Listed below is a representative round of each type.

Cartridge, QF, 18 pdr HE Shell Mark 46Non-streamlined shell filled with Amatol or TNT.
Percussion fuze No. 106 or 106E. 11.6 inch brass cartridge case with 1 lb 7 oz of Cordite
Cartridge, QF, 18 pdr HE Shell S/L Mark 13CSimilar to previous with streamlined shell. Fuze Percussion No. 115, 117 or 119
Cartridge, QF, 18 pdr HE Shell Reduced Mark 14Similar to Mk 46 but with propelling charge of 5¼ oz of Cordite
Cartridge, QF, 18 pdr Smoke Bursting S/L Mark 11CNose fuzed streamlined shell filled with White Phosphorus & Fuze Percussion No. 117
Cartridge, QF, 18 pdr Shrapnel Mark 63Nose ejecting shrapnel shell Mk 17 containing 375 bullets. Time & Percussion Fuze No. 80
Cartridge, QF, 18 pdr AP Shot Mark 3TSolid steel piercing shot with tracer
The Royal Artillery 1939-45