THE ROYAL ARTILLERY INSTITUTION. 
109 
Mr Lancaster’s gun was oval bored, the major-axis being 7*6", and the 
minor-axis 7". The rifling making one turn in 360". Tig. 3. 
One gun was sufficient for Messrs Jeffrey and Britten, as their systems 
differed from one another only in manner of applying lead to the base of the 
projectile so that it might take the rifling * Both these guns had 13 grooves 
0*10" in depth, and *846" in width, and a turn of 1 in 805". Big. 4. 
The Trench gun was rifled in 3 grooves 0*225" deep, 2*02" wide, the 
rifling gradually increased from nothing at the breech to 1 turn in 259" 
at the muzzle.t The first batch of projectiles for the Trench gun had 
three large half-zinc studs in front, supported by an iron back, and three 
small ones behind, but as the experiments went on it was found expedient 
* Mr Britten’s method of attaching lead coating chemically was adopted for the projectiles of 
the Armstrong B.L. guns, and has proved most satisfactory, 
f The sections of the several grooves are full size, those of the muzzles are on a scale of |thi 
[VOL. VI.] 15 
