Dreadnought Sustained Fire

For assault cannon or storm bolter, Ignore first jam result rolled each turn. An assault cannon will only jam if you roll 2 or more jams. Rolling 3 jams still causes the weapon to explode, destroying the arm.

For Heavy Bolter, first rol the number of total sustained fire dice you wish and then ignore the first jam from that. You cannot ignore the jam for each individual heavy bolter.