jOe,
Unfortunately, and worryingly new guns with ample barrel thickness are bulging also.
But why would you subject a barrel to a double dose of torture when once was always good enough? Plus I can't find it in the 2006 rules of proof as to why we have to double test?
Another thing, why have they changed from commercially provided ammunition to loading their own? Why did a commercial cartridge manufacturer decline to load for them?
I do not think it is unreasonable to ask for answers, unfortunately they are not forthcoming.
Over to you Diggory.