Grav-Weaponry
Grav-Weaponry are weapons that employ ancient Graviton technology, selectively altering gravity to turn the target's mass against them. Grav weapons were used by many of the Space Marine Legions during the Horus Heresy, today however the secrets of how to build and maintain them are locked deep within the vaults of mars and are even rarer then plasma guns. Only a select few know these secrets and only the most promising techmarines are trusted with them.
They come in three varieties similar to the way plasma guns do.
Grav-Pistol: The smallest of the Grav-Weapons. And comparable to Plasma Pistols in terms of how often people use them. Stats: S*|AP2|12'|Pistol
Grav-Gun: The middle sized and of the Grav Weapons.
Stats: S*|AP2|18'|Salvo 2/3
Grav-Cannon: The biggest of the Grav Weapons, Grav Cannons are only carried by Devastator Centurions.
Stats: S*|AP2|24'|Salvo 3/5
Grav-Amp: A piece of Specialist Wargear that allows any Grav-Weapons being used in the same squad as the model holding it is in to re-roll failed wounds and vehicle damage.
All grav weapons have the Concussive and "Graviton" rule. Instead of comparing Strength to Toughness when rolling to wound you instead use whatever the target's armor save is. If they have a 2+ thats what you wound them on. When rolling to Pen on vehicles 1-5 does nothing, on a 6 the vehicle is immobilized and takes a hull point. Graviton weapons have no affect on buildings.