One fun anti-gun concept i came up with is basically this:

[quote]
First of all, the nature of the forcefield itself must be explained.

It is a purely magical construct, with certain physical properties differing from ordinary matter: the reason behind this is a so-called unified energy supply. In normal matter, energy is distributed between discrete molecular and atomic bonds - in the same piece of matter, one group of bonds may break, while the other will stay perfectly fine. However, within a magic forcefield, all particles share the same supply of energy, meaning that no single bond may break or be otherwise strained without every other bond experiencing the same effect; the resulting effect is what one could call perfect dissipation, the clones either imperceptibly 'deflating' under the force of an impact, each and every bond compressing, or instantly disintegrating when the limit of their energy supply is exceeded.
[/quote]

In other words, it can tank hits regardless of how small the point of impact, and thus, how big the resulting pressure is, which works marvels against bullets, as even some rifle cartridges are roughly just twice as powerful as a simple kick.