THE ROYAL ARTILLERY INSTITUTION. 
357 
Width between trunnions ...,. 
Number of grooves ... 
Depth of grooves..... 
Width of groove at the bottom. 
Angle of the driving side..,.. 
Angle of the loading side.. 
Twist 1 turn in calibres .. 
Greatest windage over body of shot 
Windage over studs. 
268*0 mm. 
10*3 in. 
0 n 
6 
3*5 i> 
0*138 „ 
25*0 „ 
0*98 a 
70° 
70° 
90° 
90° 
24*7 
24*7 
2*9 n 
0*114 « 
1*0 if 
0*039 « 
24. There are three patterns of common shell, hut they differ in nothing 
essential except the size of the fuze hole, which was increased in 1861 from 
0*866 inch to 0*984 inch (22 to 25 mm.) measured to the bottom of the 
thread, but is still 0*866 as we measure: the depth of the thread is 1*5 mm. 
or 0*059 inch; the same change was applied two years later to the shells of 
the canon de 4. The shells of both natures which have the smaller fuze 
hole are marked A.M. (ancien modele) in red paint on the bottom. They 
are supplied to the arsenals in the rough from the foundries, with holes for 
the studs left in the cast and with the fuze hole tapped. They are there 
gauged, and studded with hammered zinc. 
Table XII. 
PRINCIPAL DETAILS OF THE 25-pr. COMMON SHELLS. 
Mean gauge over body ... 
118*0 mm. 
4*646 in. 
Mean thickness of wall ... 
18*25 
N 
0*72 /, 
Mean thickness of bottom . 
19*0 
II 
0*75 " 
Length of cylindrical part .... 
131*0 
II 
6*15 „ 
Length of ogival part... 
100*0 
II 
3*94 „ 
Total length .... 
231*0 
II 
9*09 „ 
Diameter of the holes for the studs . 
22*6 
II 
0*89 „ 
Depth.... 
3*4 
II 
0*13 „ 
Diameter of studs. 
22*0 
II 
0*87 „ 
Thickness .. 
8*0 
II 
0*31 „ 
Projection. 
4*6 
II 
0*18 „ 
Distance of first and last stud from centre 
to centre . 
94*0 
n 
3*70 „ 
Mean weight of empty shell . 
10*825 
kil. 
23*66 lbs. 
Mean weight filled and fuzed . 
11*5 
n 
25*36 „ 
Bursting charge . 
0*5 
n 
1*10 „ 
There is no shrapnel {plus a balles) for this calibre, but a common case is 
supplied, containing 98 wrought-iron shot of No. 6 size, or 1*0 inch gauge, 
in 7 tiers. 
The exterior is of sheet zinc, top and bottom of zinc castings, the shot are 
fixed by melted sulphur after being previously greased. Length complete 
about 7*7 inches, weight 24*75 lbs. It is effective up to 300 or 400 
metres. 
