Bolters – a study into the internal, external and terminal ballistics of the most iconic weapon of the 41st millennium.

1) Classification.
The ‘Bolter’ family is wide and diverse, ranging from the Bolt Pistol, the standard side arm of the Adeptus Astartes to the Vulcan Mega Bolter, a Titan mounted anti infantry weapon. What can be said to link all of these different weapon system? The key component in any Bolter class weapon is its ammunition. Bolt shells, regardless of their calibre, contain a micro rocket motor and a warhead (of many designs), making them more akin to a rocket propelled micro-grenade than a conventional bullet or artillery shell. Calibres of Bolt shells vary according to the weapon systems using them. The smallest shell of note was then 12.5mm micro deluxe round used in custom Bolt Pistols for high ranking Imperial Guard officers, the largest was 125mm ‘Vulcan Delta IV’ as used in the Mars D4 pattern Mega Bolter.

We shall be focussing on the classic bolter in this article, yet even this weapon is often misclassified by scholars, being called everything from a rifle to a sub machine gun and everything else.

Firstly a rifle is such named due to its ‘rifled’ barrel, the adding of spiral grooves to the barrel to impart spin on the round, stabilising it in flight. Many Bolters are smooth bore, so calling it a rifle would be incorrect.

A sub-machinegun is generally defined as an automatic weapon firing a pistol cartridge. As the Bolter fires its own, unique rounds, this can not also be correct.

The most commonly accepted definition is that of a ‘Heavy Assault Carbine’. Carbines, generally, have been shorter and lighter than rifles, firing a lighter cartridge to reduce felt recoil. The Bolter fits into this category with its shorter barrel and lighter recoil (for its calibre). Bolter rounds are certainly not less powerful than regular autogun rounds but due to the method of propulsion a classic bolter would produce less recoil as there is no charge to propel it out of the barrel, only its own rocket. The ‘Heavy Assault’ prefix to the carbine is in reference to the Bolters heavy rounds and sustained fire capability.

If you look at the normal usage of a Bolter by the Adeptus Astartes you will find that is generally used in the same situations the would call for Carbines for the Imperial Guard: shorter range engagements where the rapid deployment of sustained fire is more important than long ranged, accurately placed single shots.