A Primaris Space Marine Lieutenant of the Ultramarines Chapter wielding an Auto Bolt Rifle and a Bolt Pistol

An Auto Bolt Rifle is a variant of the Mark II Cawl Pattern Bolt Rifle that has been altered to make use of a high-capacity magazine and was created for use by the Primaris Space Marines. The Mark II Bolt Rifle is still essentially the archetypal firearm of the Adeptus Astartes, but now re-engineered, re-crafted and perfected for use by the transhuman warriors of the newly-created Primaris Space Marines. This pattern of Bolter was named for its creator, Archmagos Dominus Belisarius Cawl.

Like all weapons in the Bolter family, the Bolt Rifle fires small, self-propelled missiles known as bolts which explode with devastating effect. The Bolt Rifle has a longer range and slightly more penetrating power compared to the standard-issue Bolter of the original Adeptus Astartes. This Bolter variant is intended to be highly modular, allowing for variants to be easily created, depending upon tactical need. The Auto Bolt Rifle is one such variant, intended to allow the use of a high-capacity magazine by the Bolt Rifle.