This is the major problem with Polonium as a power source assuming you can mass produce it.
Weight for weight it is about 2.5 x 10^11 times as toxic as hydrocyanic acid.
Hope your battery pack doesn't leak. And talk about disposal problems.
Edit: And while recoil is an internal force it will act on the casing that holds it and that will be transferred to the person using it. In a handheld firearm any internal force will likely be transferred to an external one due to the size of the weapon and its limited mass.
[ October 30, 2003, 22:06: Message edited by: Cyrien ]