The most common cause is through under-filling the case rather than double charging. This allows the powder to burn too quickly with a resulting rapid increase in pressure. It is a misconception that the powder explodes. However a gun will if subjected to violent pressure increases for which it was not designed.
Using wrong powder doesn’t help. Many years ago at Millpool in Cornwall I was running the 600x firing point when my attention was drawn to a loud boom amongst the cracks of the various rifles on the point.
I turned to see this chap struggling with the bolt on his number four. Between us we tried everything, including a big wooden mallet from my tool-box. On closer examination I saw that the bolt was bent upwards in the middle by about 1/8th of an inch. :shock:
George (not his real name) told me that he had been using Nobel rifle number 2. I asked how much and he told me the amount. I can’t remember what it was but it was perfectly reasonable. Now you can’t (or couldn’t) get too much of that in a 7.62 case, not enough to cause damage anyway; We discussed all the possibilities and eventually George confessed that he had run out of Rifle Number 2 so had used Pistol number 2. :G
Nobel have changed the names of their powders because of lots of similar errors.
I told George to go home and do two things, first say a prayer of gratitude for the strength of his number four action and second to write to the Home Office to tell them that he had de-activated his rifle.
Moral of this particular story – read the words on the can and don’t download.
Shoot safe - shoot well.
