Badass Bolters

Badass Bolters
Anyone who has played in our larger games will probably have noticed that we tend to bring alot of bolter armed Legionnaires to the table.  We also tend to have alot of survivors, generally armed with bolters.  This seems rather unfitting from the fluff point of view that the bolter is one of the most potent standard weapons in the setting and that they seem so damned effective in the stories, but not on the tabletop.  So the Badass Bolters house rule is in effect.
Game Effect
Any "Bolter" type weapon; including but not limited to: bolters, bolt pistols, comb-bolters (only the bolter portion), heavy bolters, maxim bolters, mauler bolt cannons, vulkan mega bolters, and anyother "bolt" type weapon* gain the following rule:
Mass Reactive Shells
This weapon may change its AP to AP-.  If it does so the enemy model recieves a -1 to its Sv.

eg. a marine squad fires its bolters at a recon squad in recon armour (Sv4+).  They may either use their AP5 or change to AP- to give the Recon Marines a -1Sv bringing them to Sv5+.  Since the bolter is now Ap- the recon Marines roll their Sv vs 5+.

*Any bolt weapon using alternate ammunition rules do not gain the Mass Reactive Shells rule