THE ROYAL ARTILLERY INSTITUTION. 
89 
MUZZLE-PIVOTING GUN CARRIAGE. 
By Lieut.-Col. Gr. SHAW, B.A. 
ASSISTANT SUPERINTENDENT, EOYAU CARRIAGE DEPARTMENT. 
At a time when such efforts are being made to provide our ships and 
forts with defensive armour, and as, in such armour, the weak points are 
the necessary openings for the guns to fire through, namely, the ports and 
embrasures, it is almost unnecessary to expatiate upon the desirability of 
having such openings as small as possible. 
It is plain that so long as the trunnions of the gun remain the centre 
of oscillation for elevation and depression, the ports and embrasures in 
casemates cannot be of a less height than they now are, say 4 ft., and as 
they are 2 ft. wide, every port presents an open area of 8 ft.; and that space 
multiplied by the number of ports in a ship's side renders the main deck of 
a ship of war a very unsafe place in time of action. Bor this reason I 
turned my mind to the designing of a carriage which would enable the gun 
to have its centre of oscillation at the muzzle; and last autumn I submitted 
to the Ordnance Select Committee a drawing and specification of a casemate 
carriage for a 68-pr. 95 cwt. gun, which was to pivot at the muzzle, and to 
give 10° elevation and 5° depression, on an ordinary casemate platform. 
My proposal was favourably received, and I was given a 68-pr. gun, and 
ordered to make a carriage for it. 
I will first describe briefly the general principle by which. I obtain muzzle 
pivoting. The gun is supported on two sets of wrouglit-iron arcs of 
sufficient strength, with the centre of gravity of gun between them. The 
centre from which these arcs are described is at the muzzle of the gun. 
These arcs fit into gun-metal sockets, in the brackets of the carriage, of the 
same radii as the arcs. It is evident that if the gun be firmly attached to 
these arcs, and if these arcs be moved in the direction of the circumferences 
of circles due to their common centre, that centre, viz. the muzzle of the 
gun will remain stationary; and this is what actually takes place when 
elevation or depression is given in this carriage. 
I will now endeavour to describe the details of construction, and with the 
help of the accompanying drawings, I hope to make myself intelligible. 
The woodwork of the carriage is put together in the usual way. The 
brackets are of 7 in. teak, 3' 6" high, 7' 2" long, and the distance between 
them is 2' 1 "—the transom is teak, and the blocks, sabicu. The wrought- 
iron arcs before alluded to, which support the gun, are 6 in. wide and 2 in. 
thick, and are toothed on their front surfaces, and are of convenient length 
to suit the depth of bracket. The gun-metal sockets in which these arcs 
work are cast with a pinion-box and bearing for a shaft to go through to 
the outside of the bracket. 
[vol. iv.] 
12 
