Warpstone-enhanced rifles of any kind are the most reliable weapons developed by Clan Skryre (they're almost safe). Anytime a weapon that uses Unstable Ammunition scores a result of 1 on its roll To Hit, roll another dice. On a following roll of 1 the gun misfires and the firer will suffer a hit using the gun's Strength and save modifier. A roll of 2+ means there was no malfunction, it was just a lousy shot.