How small could you go? Modern military rifle rounds have been geting smaller and smaller over the last 100 years, from 68 cal round ball down to the .223 of today.

Part of it comes from the 'spray and pray' mentality of most grunts. If you want to do S&P, you have to carry a lot of rounds. I would rather carry 200 .223 rounds than 200 8mm Mauser rounds. Maybe they can get down to a nice 2mm round, jack up the velocity to keep it stable at 200 yards. You could carry 1000 rounds in your pack. You could blaze away at the enemy all day. I don't know how effective you would be, but that isn't the fault of the "shooter", now is it? #:^)

Plus, if all you want it for is target practice, it would be ideal. Low cross sectional area, high velocity, all it has to do it penetrate a single sheet of paper and essentially zero recoil. Ideal for target practice.

Chubber