Heligun EX17.pdf - Forgotten Weapons

IGNITION
FURTHER DEVELOPMENT NEEDS
HTC-AD 66-29
The percussion primers of the 7. 67mm ammunition are fired by mechanical
impact on the lower barrel firing pin and hot gas pneumatic impact on the
upper barrel firing pin. Ignition stoppages fall into two main categories,
because of the differences in the firing mechanisms employed. The reli­
ability of the ammunition itself has proven to be excellent, and the solution
to ignition stoppages will be found in increased reliability of the weapon
firing mechanisms.
Lower barrel (first-fire) ignition stoppages are relatively rare and are
caused by either:
L Low counterrecoil velocity, or
2. Unusual hammer excursions
The first cause will be controlled by improved parts life and cycling
o£ the recoiling parts and revolver, as discussed in a later paragraph.
Item 2 requires investigation of causes and their subsequent elimination.
Upper barrel (last-fire) ignition problems are caused by temperature and
fouling effects ase.ociated with the gun gas firing mechanisms. Changes in
shape and fit of parts will eliminate this problem. Currently, one-third
of the stoppages are of the ignition type.
A-2