I suspect you're going to need a lot more than 750 fps to stabilize one of those bullets, Sam. And I think a Blodnob valve could do it. Not as familiar with the .177 capabilities, but I can push a 28 gr. .22 EJ over 1300 fps with my Blodnob valve and a 24" barrel. That's with a 110 gm. hammer and stock hammer spring. Best I can do with an 80 gm. hammer and stock spring is about 1100 fps. Just got some .177 EJ's but haven't tried them yet. But 1100 fps with .177 Kodiaks is no problem. And that's from a 12" barrel. I need to get some heavier hammer springs, I think the stock spring is limiting my capabilities somewhat. Even at that, Sean's valve is far more powerful than I can take advantage of with the pellets that are available in .177 or .22. Maybe a .25 barrel and the 42 gr. EJ's would be more in line with what it can do on the high power end. I've considered a similar idea to what you want to do, but in .22. Have a barrel machined that will handle .223 dia. bullets. Lots of options in that caliber and size in the 35 to 50 gr. range. Of course, after all that, you probably aren't going to do much more than duplicate what a .22 rimfire can do, so I'm not sure what the point would be :-). But I'll be really interested to hear about it if you proceed. Later.
Dave
