I would also look at the 6mm Mach4 to really maximize the concept.
Ross Siegfried built one and wrote about it. I think he got 4,000 fps with the 100gr.

I read that Rocky Gibbs was leery about the 240 but it may just have been due to the powders available then. It was along the lines of pressure excursions like those reported in the 243 but amplified in the Gibbs. Apparently this didn't occur in the 25 or not as much.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli