Large calibre cartridge ignition question


I was repositioning my largest cartridge, and became curious how the height of the ignition stalk is calculated. It is obvious that it is made to deliver the fire into the middle of the propellant charge. So, is it just the half of the gun powder level or there is more to it?



I can’t say that I’ve ever seen it documented, but my military mind tells me that the length of the primer and the amount and compostion of the igniting charge are based on tests.

Or, maybe someone simply said, “That looks about right.” ;) ;)



The proper type of primer used would not be easy to tell. For wich propellant the primer is needed? Wich projectile is going to fire? I’m sure there are a lot more important questions.

Testing is the only way to find out what’s the right primer for the job.
Elements of Ammunition tells about some tests,

Sand Test.
In the sand test the detonator is assembled in the predescribed testing fixture, Fig.23, and initiated by a standard procedure.The detonator must crush a minimum amount of sand of a specified grade. This amount is a measure of the “force” or crushing action of the detonator and an indication of brisance. The test definitely distinguishes between a high- and low-order detonation. It is usually applied to detonators wich are initiated by flame action rather than by the stab action of a firing pin.

Lead-Plate Test.
In the lead-plate test the detonator is assembled in the prescribed testing fixture and initiated by dropping a ball of specified weight a certain distance on a firing pin. The detonator must function on the first drop of the ball and pierce the lead plate to not less than a required minimum diameter, Fig.24. This test measures sensitivity, functioning and also “force” in that it distinguishes between high- and low-order detonation. It is applied to detonators having primer mixture and is initiated by stab action of the firing pin.