Shootall,
My apologies. After reading my response a day later, it does read like I was bustin' your chops. Sorry, that was not my intention. It just looked like your data, at least for 358 win, was a little slow.
Boring out a 348 to a 358 would be an interesting idea. So long as you stayed away from pointy bullets, and kept loads to 348 pressures, since you'd have to keep the 348 brass and neck it up. Even so, same pressure and bullet weight, with a bigger diameter gets you a faster bullet.
Andy