TM 9-1375-213-12
(4) If the misfired charge is located in a stemmed
the firing pin and then actuate the igniter again.
borehole, or if placement of stemmed charge makes
method (3) above, impractical, follow either procedure
(2) If two or three retries with the M81 do not re-
listed below.
sult in it firing, cut the shock tube, replace the igniter
with a new one and repeat firing procedure.
(3) Another misfire mode with the M81 is that the
WARNING
primer fires, hut blows the shock tube out of its securing
DIGGING INTO CHARGE MAY INI-
mechanism without firing it. (This would usually be due
TIATE CHARGE. CHECK ON DEPTH
to the shock tube not having been properly inserted and
AND DIRECTION OF BOREHOLE
secured in the igniter.) The corrective action is to cut
DURING DIGGING TO MINIMIZE
approximately 3 feet from the end of the shock tube, re-
DANGER OF STRIKING CHARGE OR
place the igniter, and repeat firing procedure.
PLACING A NEW CHARGE TOO FAR
AWAY TO INDUCE DETONATION.
(4) If the igniter appears to have functioned prop-
erly (primer pops and smokes), but the charge did not
fire, cut a one-foot section from the shock tube starting
(a) Procedure No. 1.
approximately six inches from the igniter. Hold the one-
foot piece of shock tube so that one end is over the palm
1. Carefully remove stemming by nonmetallic
of your hand and gently blow through the other end. If a
or nonsparking tools, or if available, by a stream of com-
fine powder is blown from the shock tube, it has not
pressed air or water.
tired. If this is the case, install a new igniter on the fresh-
ly cut end of the priming shock tube.
2. Dig until charge is within one foot of being
uncovered.
(5) If the igniter/initiating element functioned
properly and if no fine powder was blown from the shock
3. Insert a new, primed 2-pound charge on top
tube in the previous step, or the shock tube was heard to
of misfired charge.
fire or its flash was seen, observe the standard half hour
waiting time before going downrange to check the next
4. Detonate a new 2-pound charge. When ever
element(s) in the priming train.
possible, detonating cord should be used to prime either
(6) After the half hour waiting time has past, proceed
through 2-12).
downrange and check the detonator of the first compo-
nent in the priming train. If the detonator has not fired,
(b) Procedure No. 2.
attach an identical component (M12 or M13) to the shock
tube (or detonating cord) of the uninitiated second com-
1. Carefully dig a new hole to within one foot
ponent close to the unfired detonator of the failed com-
and to the same depth as old hole.
ponent. Lay out the shock tube of the replacement
component back to the site from which the shot is to be
2. Place a new, primed 2-pound charge in new
initiated and repeat the standard initiator attachment and
hole.
firing sequence when it is safe to do so (range clearance
received, etc.).
3. Detonate new, primed 2-pound charge. Fol-
low instructions listed in (a)4 above.
NOTE
After the charge has been fired, deal with
c. Misfires with Shock Tube.
the unfired relay cap and its attached (par-
tially fired) shock tube in accordance with
(1) The most common cause of a misfire in a
standard procedures for disposing of an un-
shock tube priming system is the initiating element, usu-
fired blasting cap.
ally an M81 Igniter. The most common failure with this
item is the primer not firing. The corrective action is to
recock the M81 by pushing in on the pullrod to re-engage
Change 18
2-4.7