542 FAILURES AT PRACTICE WITH T. & P, FUZE MARK IV. 
bullets may set back on to the powder charge witb sufficient violence 
to fire it. 
17.—-If the escape hole is completely blocked the flame will, when 
the gas has got up sufficient pressure, burn up the leather washer and 
run along the surface of the composition causing a short burst. 
19. —Bad clamping may contribute to a long burst if the clamping 
is not sufficient to prevent the ring being pulled round, when the 
safety pin is drawn out, as explained in (3). 
20. —If the escape hole is only partly blocked, that is, so as to allow 
a certain amount of escape, or so blocked that the obstacle is driven 
out when the gas attains sufficient pressure, the composition will, in 
the former case, burn more slowly all through, and in the latter case, 
slowly at first and at the normal rate when the obstruction is blown 
out. The slowness of burning is caused by the increase of pressure, 
and in this case, as the washer is not burnt, the flame can not behave 
as in (17). 
Fuzes are now sometimes carried set at 2 and in that case there 
seems to be great risk of ranging shots being fired with the time pin 
drawn and the ring so set ; indeed there is no doubt that this is 
frequently done, and the fact that when fuzes are set at 2 the loops of 
the two pins come together renders it the more likely to occur. 
It is proposed to insert the time pin so that the loop will be at a 
different point, but I think that the present is the best position for the 
pins and that the men should be trained always to draw both pins and 
to set the time ring at the safety point f, or a little beyond it towards 
18, when firing percussion shell for ranging, the fire being slow there 
will be plenty of time for the setting. If both pins are invariably 
drawn the action will be done without thinking and become automatic, 
and if there is any action in the service of the gun that should become 
automatic it is that of pulling out the pins, whereas if the men are 
taught sometimes to draw out the pin and sometimes not, they may 
not draw out the time pin when necessary or may draw the wrong pin. 
The list of possible causes of failure may seem at first glance a rather 
formidable one, but most of them are possible only, and will very 
rarely be met with when the fuzes and shell are in actual use. There 
are really only three which need be considered and guarded against 
usually in actual practice, viz., not drawing the pins, or drawing the 
wrong one, bad setting and bad clamping. 
I may seem to have laid undue stress on the possibility of the time 
ring being pulled round when drawing out the pins, which can only 
happen when the clamping is defective, but a number of short bursts 
occur which can not be accounted for on any other supposition, they 
are so far wrong that they can not possibly be attributed to inaccurate 
setting or irregularity of burning. 
In writing the above, I have had the 15-pr., and 12-pr. 6 cwt. guns 
in my mind, but most of the remarks are general and, though I have 
probably stated little that is not already well known to battery officers, 
