Bolt

Due to the new "Weapons" articles, this page now serves the goal of defining and specifying the ammunition of "Bolt Weapons," such as the Bolter or Psycannon. Not that it does this well, mind you.

The basic Bolt used in a Bolter is an armor-penetrating, explosive, rocket-boosted bullet based roughly on modern-day gyrojet ammunition technology. The term "Bolt" is actually Imperial slang, and the terms "shell", "round", and "Bolter ammo" all apply to that very same projectile. Since bolt rounds vary in size and manufacture between different types of bolt-based weapons, different patterns of bolt-based weapons, and different factions wielding the bolt-based weapon is question, this preamble will create a general idea of what a Bolt is, so that the variants can show you how they differ. By design, Bolt shells penetrate the outer armor of a target, and then explode in a concussive and shrapnel-filled blast once inside the target. The idea is to maximize the amount of squishy flesh that gets liquified and dun-goofed when the shell explodes, literally ripping the target apart. They use a rocket charge, not a single explosion, as propellant. This is pretty much all that is similar over EVERY bolt design.

It should also be noted that the term "Bolt" can also refer the ammunition used by Bolt Throwers in Warhammer Fantasy, which are big friggin' arrows.

Bolts are also a type of primitive lock mechanisms that can be attached to doors and hatches in fantasy and modern settings. Because not everything is about 40K, you know.

Bolter

Bolters are submachine guns, if submachine guns were giant blocks that fired 20mm armor-piercing rockets. The bolts (read: rocket propelled explosive bullets) are about as big around as your fist, and detonate upon impact. Imagine getting a grenade fired into a random orifice at mach 2, which then detonates. It literally violates everything everything in the immediate vicinity (and not in the good way). But of course, it doesn't just stop there, now does it? No, it's a mother fucking assault rifle too, so the bitch has seven more rounds like it following it, and they all think your head isn't "mooshy" enough, so they all just kinda blow you up. Does it end there? NO, of course not. Bolters are used by Spess Muhreens, so they're also followed up by a nine foot tall giant in a suit of armor that even Oprah Winfrey would have no problem hiding behind, and they proceed to kick your ass with their giant fucking swords and uber-fists.

Now you're fucked.

Bolt Pistol

Bolt Pistols, are like a Bolter's Daughter. But the really slutty one, so everyone can have go with her. These things are about the size of a modern-day sub-machine gun. All Commissars have them, and they'll all be like, "HERESY" while you're on the shitter, or, "HERESY!" while you're shooting at the range, or doing your girlfriend, or getting severe head wounds checked out by the medic. Spess Muhreens use them, too. What's derpy is that Bolt Pistols have NO drop in stopping power from the aforementioned Bolter, so the Bolter is kind of a stupid weapon. Why would you carry a heavy Boltgun when a Pistol is just a good? Because in the 41st Millennium there are more fucktards per 1000-head of population than in, say, Alabama. That and a regular Bolter has the tendency to break a regular dudes arm with the recoil, unless they use bionics or are sufficiently manly.

Bolt Pistols fire a smaller shell than their heavier cousins, giving them even less recoil because the propellant has less time to fill the shorter barrel with gasses before exiting. This in turn leads to a lighter payload. Since the potency of Bolt weapons comes from their explosive charge and not the shell's velocity, the amount of propellant was reduced to keep the charge the same size. Similarly, the Bolt Pistol is less accurate than the Bolter is because the Bolter has inbuilt targeting devices accessible by Power Armour helmets, and the Bolt Pistol has less rifling to keep the bolt shell straight. In all the time the Imperium had, hey never developed smaller bolt shells that spin themselves. Go figure. It's not like the Commissar cares, he always fires it point blank anyway.

Heavy Bolter

Heavy Bolters are basically machine guns on PCP. They are a Heavy Weapons choice for Guardsmen, who require a two-man team just to operate it. However the giant Space Marines wield them like a fat baby's lollipop and have even attached bayonets to them. If you weren't squishy enough, getting hit by one of these will make you squishy...er...

These Bolt shells are significantly larger in size compared to normal bolts. Using the fist analogy, they are Space Marine fist sized, not Guardsman fist sized. This size increase allows for both more propellant and more explosive, giving the Heavy Bolter enough power and range to blow apart light mechs, tacticals, and ogryn-sized beasts with scary efficiency.

Variant Ammo

The Bolter has dozens of different types of ammo. While the standard DERP (Double-Explosive, Raker-Purpose) Sickle-bolt is the most common, and are commonly mistaken for the similarly common HERP rounds (High-Explosive, Raker-Purpose). They also come in Dragonfire anti-cover incendiary rounds, long-range anti-armor rounds (the Kraken-pattern Penetrator round, which sounds more like a sex toy than a munition), poisonous Hellfire-pattern rounds wherein the explosive charge has been replaced with a chamber of (Poisoned 2+) bio-acid, and the Vengeance-pattern short-range anti-Power Armour rounds (because they you get "vengeance" against Traitor Marines! Creative, isn't it...). Vengeance rounds can also melt your own guy, because they suffer from the "Get's Hot!" rule.

Note that on the tabletop, ALL of these give some benefit: Hellfire rounds always wounds on a 2+ (excellent for killing Carnifexes if anyone would be using those anymore that is... Of course, they do rape Biotitans). The Dragonforce bolts ignore cover saves and the sex toy pattern has a range of 30 inches and slightly better AP value. The Vengeance rounds are AP 3, but at a range of 18 inches, and they can make your Bolter overheat into your face like a Plasmagun.

Magic Ammo

"Yes my friends, Bolters can even fire magic."

Psycannon Bolts, a form of ammunition designed to make Bolt weapons more like Psycannons (and thus be more ass-kicking). They use similar warheads as described in the Psychannon Rounds section below in order to achieve their Psycannon-like properties. They grant a given Bolt weapon slightly better armor-penetration and allow it to bypass shielding and supernatural protections (until that was nerfed by Matt Ward, giving any such weapons just a strength bonus of +1).

Psycannons themselves use rounds mysteriously called Psycannon Rounds. Since the gun itself creates the psychic charge, nothing is really notable about these rounds besides the fact that they lack an explosive charge altogether. They take the psycho-active waste material produced by the Golden Throne's arcane operation and load it as the warhead instead. This allows the Psycannon to turbocharge the bolts with psychic energy like intended. There is some debate as to whether Psycannons actually charge the power into the catalyst, or if the psychic fields activate the power within the round itself. With the passing of Wardstorm Matteaus over Imperial data archives in Alpha Centauri, no one may ever know the real truth. Either way, what is know is that Psycannons are loaded with the Emperor's poop.

The Chaos Marines who worship Tzeentch are given ammo called Inferno Bolts, which cause Bolter rounds to cut through even Marine armor with ease, and cause Necron players to break out in hives. These actually magical bursts of life force and fighting spirit from the Rubric Marines who use them, seeing as they are just souls trapped in armor and have nothing better to do with their life force.

Kai Guns fire conventional Bolts, but they are also a psychic catalyst; imbuing the rounds with the hatred and malice of the firer, increasing damage output exponentially. Or... it used to anyway, before it got nerfed.

In Apocalypse, you can take a Chaos stratagem called a Daemon Shell, which is a Bolt round with an uber-angry daemon bound to it. This effectively takes the Bolter it is being used in and turns it into a 7"-Blast-hurling weapon of short-range mass destruction. The binding ritual is supposed to take a geologically long time, so it really sucks when you waste the time (and stratagem) on a shell that could miss and blow you up. Badly.

In Summary

 Be a part of The Imperium of Man, and you get these weapons. 
 Chaos is not your friend. 
 The Emprah is your Savior.
 *BLAM*