Many thanks for the info. I was thinking of using an existing .338 bore barrel to avoid having one custom made. I have discovered that a couple of US gunsmiths, (Fred Zeglin at Z-Hat and Charlie Sisk) have .333 reamers although there will likely be some border issues as I am in Canada. If I were to get a Canadian gunsmith to do it, I would almost certainly have to buy the reamer as they are not that common (!!) I figured that the 'smith might be able to chamber it for the Jeffrey and then enlarge the neck area to accomodate the larger neck.

The next thing is to find out whether the Martini action will accept the Jeffrey cartridge. Having the cartridge dimensions will help. I don't think pressure will be a problem.

Guess I should break down and buy a copy of COTW as it is something every "gun nut" should have.

Stuart