540 FAILURES AT PRACTICE WITH T. & P. FUZE MARK IV. 
14. Weak time safety pin (thousands previous to 152 only). 
15. Defective fuze. 
16. Weak shell. 
1 7. Escape hole blocked by any foreign substance. 
C.—Long bursts may be due to 
18. Bad setting. 
19. Bad clamping. 
20. Escape hole partly blocked by foreign matter. 
The reasons for some of the above are clear, but others seem to 
require some explanation ; taking them as numbered 
1. —The safety pins are sometimes broken off at the eye, either 
whole or half of the split portion remaining in the hole, by the No. 3 
not pulling them straight out (see remarks on 3), he thus cuts them 
against the sharp edge of the hole. If half the time pin were left in 
the hole it would probably be sheared on firing. 
2. —A defective fuze may cause a blind either from non-ignition of 
the time ring, which is almost unknown, or from failure of the 
percussion action either from (a) the needle being blunt or soft or the 
brass disc covering the detonating composition too thick or hard ; (b) 
the centrifugal bolts not drawing clear of the slot in the body, or (c) 
the safety pellet and ball may not drop and clear the needle pellet, but 
a failure has never been known to occur from this cause. 
3. 12. 19.— Bad clamping; this appears under all three heads, 
A, B and C, and may account for any form of failure. 
When the No. 3 is pulling out the safety pins he seldom pulls them 
in the direction of their length, as they are not set vertically to the 
ring and body but transversely across them. 
If the fuze is not well clamped the ring may be pulled round to any 
point. I found that with the ring set at 2 and the nut clamped only 
with the hand or lightly with the key and the shell held as a man 
would usually hold it, I generally pulled the setting round to a point 
between 0 and the safety V, others pulled it over the safety mark and 
on to the long setting beyond it. If the setting is at 0 the burst is 
just outside the gun, 20 to 40 yards probably; if at a point about one 
third of the way between 0 and V the burst is almost instantaneous 
and is in the gun ; if from this point to about one third of the way 
between V and 18 the time action is blind, the fire hole leading to 
the magazine and percussion part of the fuze being covered by the 
bridge, but if the ring is pulled still further round the burst becomes 
long or short according to the extent it is displaced. Also in lifting 
the shell out of the magazine, the No. 3 may give the ring a twist and 
displace the setting, if the clamping is not properly done. 
4. Weak or defective shell may cause a blind in two ways. 
