I'm looking at a project for a long range rifle for small deer (low volume shooting). .22 centerfires are legal in my state and I would use partitions or X's. What's the fastest in a .22 to 7mm dia wildcat? Efficiency is not an issue. As someone once said; "They make new barrels every day."

Look at Pac-nor's specialty chamber list, www.pac-nor.com. They chamber a 6.5x50bmg and a few other small bores that are just hard to imagine.

There are some incredible continental cartridges which are actualy factory. The Vom Hoffe series includes a .22. It positively dwarfs a 5.6x57. There's also something called a 5.6x61rimmed which sends a 77gr .22 bullet at 3,700fps and would do pretty well in a ruger no1 I bet. Then there's the 6mm Freres, 6.5x68 etc etc

Not all high velocity cartridges are from the US or wildcat. The continental manafacturers actualy make this stuff. It would be good to hear from someone who actualy uses some of these weird and wonderful offerings.

With regards to 22 cal, the 22-6mm Imp seems to be at about the upper end of usable powders with regards to reloading.
A magazine write up on this caliber was getting 3800+ fps with 80 grain match bullets, supposedly with no signs of excessive pressure. The article was before Reloader 25 became available, so there could be a bit of gain even above the original velocity figures.
The only head scratcher I see is that the hunting bullets are a bit lighter than target bullets right now, and I have not seen any velocity figures using the lighter bullets.

For raw speed in an easily obtainable case, consider the .22-284. Rick Jamison of Shooting Times has worked with it, and would be a good source of info.