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| Space Marine 2 |
The Boltgun, commonly known as the Bolter, is one of the most iconic weapons in the Warhammer 40k universe. It is most often associated with its primary users—the Space Marines (Adeptus Astartes) and the Adepta Sororitas.
This weapon is surrounded by legends and myth, said to have been designed by the Emperor of Mankind himself for the purpose of conquering the galaxy in humanity’s name. Naturally, this leads to the question: How powerful is a single Bolter shot?
To answer this, we will analyze the ammunition used by this legendary firearm, relying on information from official Warhammer 40k lore, codices, and novels. In areas where no direct or explicit data is provided, we will complement the analysis with real-world ballistic knowledge, allowing us to establish a reasonable estimation range.
Official Data
According to official information:
- The Bolter has a caliber of 0.75 inches (20 mm), while the Heavy Bolter uses 0.998-inch (25 mm) rounds.
- Projectile velocity is described as hypersonic, with a minimum of 1700 m/s. Other mentions reference slightly slower rounds at 1500 m/s, about 13% lower.
- Several ammunition variants exist, but for this analysis we will use the standard bolt round, which includes:
- A solid-fuel rocket booster
- A hardened diamantine penetrator tip, allowing the bolt to pierce most armor before detonation
- A micro-delay fuse, detonating fractions of a second after impact to ensure penetration
- •A super-dense “depleted deuterium” core, a fictional equivalent to real-world depleted uranium (density ~19 g/cm³), improving penetration
- A main explosive charge, though the exact amount is not officially specified
- Projectile mass
- Type and amount of explosive filler
- Penetration properties of diamantine as an armor-piercing material
To fill these gaps, we will use real-world projectiles with characteristics similar to Bolter and Heavy Bolter rounds.
Bolter
Despite the weapon’s iconic engineering, most of its destructive power comes from its ammunition—specifically the standard bolt, which combines armor-piercing and explosive properties.
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| Bolt Rounds and their description. |
In the real world, 20 mm autocannon rounds serve as a good analogue. These are used as anti-aircraft ammunition or as secondary armament on fighter jets, helicopters, and armored vehicles. Examples include:
- The 20 mm M61 Vulcan rotary cannon used on F-16 and F/A-18 aircraft
- The 20 mm M197 electric cannon mounted on AH-1 Cobra helicopters
Although these weapons operate differently, their projectiles generally reach velocities of around 1040 m/s, which is lower than the Bolter's hypersonic speeds. However, their projectile mass remains consistent, averaging 100–102 grams (0.1 kg) across most 20 mm ammunition types.
Given this consistency across real-world weapons, using a 0.1 kg projectile mass for the Bolter is a reasonable and practical assumption for further calculations
KE = 0.5 × 0.1 × 1700² = 144,500 joules of kinetic energy—enough to penetrate roughly 20 cm of steel.
Despite the projectile’s high impact energy, we still need to determine the type and amount of explosive filler inside the bolt. For a 102-gram projectile, the explosive content is typically around 10.7 grams, approximately 10.4% of the total mass. The remaining question is what type of explosive is used.
Modern 20 mm rounds usually contain RDX (cyclotrimethylenetrinitramine), a powerful military explosive equivalent to 1.5× TNT. However, since Bolter ammunition is described as containing super-dense material, it is reasonable to assume the use of a more advanced, higher-yield compound. A plausible option is Octanitrocubane (ONC)—the most energetic practical military explosive—rated at 2.38× the strength of TNT.
Knowing that 1 gram of TNT = 4184 joules, then:
1 g ONC = 9957 joules
Thus, the 10.7 g explosive charge yields approximately:
10.7 g × 9957 J = 106,500 joules
Adding both components:
- Explosive energy: 106,500 J
- Kinetic energy: 144,500 J
Total energy per standard Bolter round ≈ 251,000 joules
For comparison:
- A .50 BMG (12.7 mm) round delivers up to 20,000 joules, making it 12.5× weaker than a Bolter shell.
- A 30 mm GAU-8 Avenger round produces ~200,000 joules, about 25% less than a Bolter shot.
Heavy Bolter
Moving on to its larger and more powerful counterpart, the Heavy Bolter, with a 25 mm caliber, we find that it shares nearly all structural and functional characteristics of the standard Bolter. Using the same methodology, we can compare it to real-world autocannons. Examples include the M242 Bushmaster (25 mm) used on the M2 Bradley, or the Rheinmetall KBA, the NATO standard. These weapons use projectiles with very similar specifications:
A 25 mm round typically weighs 180 grams and carries about 32 grams of RDX as explosive filler. Following the same approach as with the Bolter, we will use Octanitrocubane (ONC) as the higher-performance substitute.
Kinetic Energy:
KE = 0.5 × 0.18 × 1700² = 260,100 joules
Explosive Charge:
32 g × 9957 J = 318,600 joules
Total Energy Output:
260,100 J + 318,600 J = 578,700 joules per Heavy Bolter shot
For comparison, the Bofors 40 mm L/60—a World War II naval autocannon—delivers around 511,000 joules (combined kinetic and explosive energy).
Based on ballistic comparisons and known specifications, a standard Bolter round delivers around 250,000 joules, while a Heavy Bolter shot reaches nearly 580,000 joules. These energy levels match the destructive impact described in Warhammer 40k lore, showing why Bolter weapons are feared across the galaxy.
These results remain consistent with the descriptions provided in Warhammer 40k lore regarding the devastating effects of Bolter and Heavy Bolter fire on human targets. Always remember to respect the holy might of the Bolter, crafted by the Emperor Himself.
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