theres quite a few more problems with Polonium than that, but you basically summed it up. its still a darn neat prospect.
Anyhow, I'm not sure your on top of the whole internal force / external force thing.
in a conventional firearm, force is exerted on a projectile. a bullet and gasses exit the weapon, exerting an equal an oposite force on the weapon and wielder.
in this hypothetical laser, the force exerted by the light leaving the weapon is negligable, and thus the equal and oposite newtonian force resulting from the projected beam of light is also negligible. the gasses, while moving at high pressure and velocity within the weapon, never leave it. therefore, force should not be exerted on anything outside the weapon.
Granted, you will need sturdy components inside the weapon to contain those gasses and to channel them around, but there should be no felt force by the operator.
the best practical example that i can come up with, is a solonoid. if a solonoid is sitting on a table, and is repeatedly activated, the coil and the cylinder will both experience force from each other, but the net motion of the entire object should be zero.
but i could be easily be missing something obvious.
edit: dont you wish you had some?
http://pearl1.lanl.gov/periodic/elements/84.html odds are, you do! I just saw an article indicating that commercially grown tobacco contains the stuff!
[ October 30, 2003, 22:35: Message edited by: Puke ]