Under the rules if a hex is Bombarded, all friendly adjacent hexes are subject to possible "Friendly Fire". This means that if a mortar or other Bombardment capable weapon fires at a hex adjacent to it, the firing weapon can potentially be hit by Friendly Fire.
I completely agree with the Friendly Fire rule in general. I think this is an excellent rule to prevent constant Danger Close artillery barrages. I think, however, the rule does not work when it can mean that a weapon can land a round on itself. I am going to propose a couple of fairly simple house rules to avoid this problem.
Proposed House Rules:
1. Light and Medium mortars (< 90mm) may ignore their own hex when determining Friendly Fire.
2. Heavy mortars (> 90mm) have a minimum range of 2 hexes. They are now prohibited from firing at an adjacent hex. The minimum range for many of these heavy mortars is at least 500 m. (about 2 hexes). This rules avoids the mortars blowing themselves up and adds realism without much complexity.
3. Infantry guns and artillery pieces can't really "Bombard" something 200 m. away. It's really point blank aimed fire. Infantry guns and artillery pieces are now allowed to convert to use Direct Fire. An IG or ART wanting to Direct Fire may do so at an adjacent hex with a Direct Fire value equal to half (rounded up) of their Bombardment value. This one half value represents something of a penalty for using this capability. And does now allow for these weapons to use Opportunity fire at moving adjacent units.