One for the Gun Designers...

[Robin128]

I can't remember where I read it but in terms of tolerences (remember now...I am not an engineer or 'smith) there are staggering variations on the centrality of the bore with reference to the outside surface of the barrel.

:)

[The Gun Pimp]

Rob,

Very true - one must always 'clock' on the bore when setting up a barrel.

Cheers
Vince

[Ovenpaa]

It makes me wonder.... if the bore was sufficiently out of line and the barrel hot enough then uneven expansion would distort the barrel. It would have to be a pretty awful barrel and a lot of rounds through it, so maybe more of an issue with obscure early post war Eastern block machine guns than the latest Border offering.