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 Elbows wrote:
Both of these pictured rounds are .50 caliber. One fits in a pistol...the other can fly 2+ miles.

Think you might be getting that .50 Beowulf confused with .50 Action Express, as Beowulf is a rifle round with comparable overall length to .223/5.56. Which actually further highlights your point, if nothing else.

I'd also point out that in addition to the second dimension (denoting overall length) to specifically identify a caliber, there's also loading to consider. .38 Special and .357 Magnum use the same projectiles and are nominally the same round, but with the .357 loaded considerably hotter, with a minor increase in case length solely to prevent chambering in a revolver only intended for .38 Special. .380 ACP is a lighter loading of 9x19. .460 Rowland is just a very hot-loaded .45ACP, and uses the same magazines.

So when we're talking 20mm, that could be anything from the 20x42mm which is a 110g projectile launched at a leisurely 1000fps, to the 20x138mmB which is a 120g projectile at a screaming 2,950fps. The latter has just under ten times the kinetic energy of the former, and over triple the momentum (meaning over triple the recoil force). As you said, it's not the caliber that tells the whole story.

All that said: Even if bolters are basically just select-fire Neopups/XM25s with additional onboard propulsion and sci-fi explosive charges, that seems suitably lethal to me, and appropriately difficult for an unaugmented human to handle without being completely impossible to shoulder-fire like a conventional 20mm autocannon.

Yep, you're right. I was thinking of the AE. But yes, same concept.

I think in the end that the model designer simply isn’t familiar with real weaponry and went with rule of cool.

In-world, blame the Admech. They probably included sacremental features dictated by the Administratorium to be a proper “holy Bolter” regardless whether it made sense or not (esp. the scope being blocked by the “requisite” iron sights that are a Technical requirement for a gun in the Admech holy texts).

Ya’ll are getting too deep into the weeds to justify an artistic screwup.

To be fair, it's not anywhere near as bad as the bolt action sniper rifle with an enclosed bolt...



I think it's fair to say that most if not all of GW's sculptors know feth-all about the way firearms work.

Charistoph wrote:

VictorVonTzeentch wrote:The weapon in these videos is a 20mm Rifled Grenade Launcher.

True. I was looking at more of a direct fire round than an AoE Weapon, as the Boltgun generally is not considered firing grenade equivalents.

Indeed, how ever the Inkunzi is a "Grenade Launcher" in thats just what its classified as. It fires more like a rifle, as it has a flatter arc and more velocity than a 30 or 40mm Grenade. Plus it has more than just HE. It has SAPHE, AP, HE.

Cronch wrote:

The closest we currently have to a Bolter is probably the Inkunzi (Neopup) P.A.W., which is a 20x42mm cartridge.

I'd say the XM-25 was the closes, firing 25mm explosive rounds and being fed from a 5-round box magazine. And one of the complaints that led to it's cancellation was small explosive payload.

25mm would likely be closer to a Heavy Bolter. Also the weapons I mentioned fires HE, SAPHE, has a bigger mag, uses a round closer in size.

Elbows wrote:Remember, when we're discussing stuff like caliber, 20mm is only one of the attributes. If you said "Oh, this is 20mm..." that just means the diameter of the round is 20mm. It doesn't mention or address the powder charge or length/weight of the actual round.

So a 20mm cartridge could be fat and short, with less powder/range/power, etc. It's why we refer to normal rifle cartridges by their full name in many instances, such as 5.56x45 or 7.62x39. The latter part describing the length of the powder cartridge behind the round.

Both of these pictured rounds are .50 caliber. One fits in a pistol...the other can fly 2+ miles.

Yep, hence why I specifically called out the 20x42mm for people. Its a shorter round.

 Charistoph wrote:

Inquisitor Lord Katherine wrote:I know. I may be a girl, but I would say I know more about 20th century conflicts and weapons than your average man.

Nothing was addressed to your sex, so no need to bring it up. I was more addressing how a 20mm is mentally thought of, and maybe it's just because I'm an aircraft enthusiast, I usually see the 20mm as an aircraft weapon more than a ship or tank weapon. The other paragraphs were more for general address.

Sorry [a little bit], and was a little bit cranky that somebody felt the need to explain to me what a 40mm Bofors [and etc.] was. I despise it when people explain to me basic things that I already know.

I'm a tank & ship person [despite being an aerospace engineer], so I think of a 20mm gun as a very little gun.

 Elbows wrote:
To be fair, it's not anywhere near as bad as the bolt action sniper rifle with an enclosed bolt...



I think it's fair to say that most if not all of GW's sculptors know feth-all about the way firearms work.

Hah, I linked the same gun on the previous page! Bolters are fine. That Palanite rifle though...

the bolt shell casing is 20mm as well ( pictures design it that way) but I think there are a couple of hand waves for that one:

1) SciFi gunpowder requires less
2) it's only an initial propellant, so doesn't need a lot to get it going


A more interesting physics question for me, is the shuriken catapult. It's effectively a gravity wave powered coil gun. There are no physics I know of that will explain why the description of the weapon results in a 12" range...

The 12" range was an arbitrary random decision to try to differentiate Eldar or make them worse than Space Marines.

 Elbows wrote:
The 12" range was an arbitrary random decision to try to differentiate Eldar or make them worse than Space Marines.

Not at all, you gotta remember how they stacked up at the time of that change for 3rd Ed.

Bolters could fire twice up to 12", or once up to 24", but in either case only if the marine stood still. AND the marine couldn't charge afterwards.
If the marine moved, he could fire the bolter ONCE.

The Shuriken Catapult allowed the user to move, fire twice at 12", AND charge.

The major comparative issue is that over the editions, the rules regarding the Bolter have slowly improved, while the Shuriken Catapult has basically not. (which is a shame)

Regardless of it's change...they were giving a Toughness 3 model with crap armour a 12" gun...as if they "wanted" to charge after using it. Eldar Guardians are as weak as guardsman when it comes to firepower. What they want is stand-off distance. They want a 24" gun. The old lasgun would be better in most circumstances than the current Shuriken catapult. The Shuriken Catapult should have stayed a semi-expensive upgrade, and lasguns should have continued in the basic Eldar lineup.

 Elbows wrote:
Regardless of it's change...they were giving a Toughness 3 model with crap armour a 12" gun...as if they "wanted" to charge after using it. Eldar Guardians are as weak as guardsman when it comes to firepower. What they want is stand-off distance. They want a 24" gun. The old lasgun would be better in most circumstances than the current Shuriken catapult. The Shuriken Catapult should have stayed a semi-expensive upgrade, and lasguns should have continued in the basic Eldar lineup.

Yeeeaahh, I think they specifically didn't want lines of immobile Eldar, so just on principle I tend to prefer their general idea.

 Insectum7 wrote:

 Elbows wrote:
Regardless of it's change...they were giving a Toughness 3 model with crap armour a 12" gun...as if they "wanted" to charge after using it. Eldar Guardians are as weak as guardsman when it comes to firepower. What they want is stand-off distance. They want a 24" gun. The old lasgun would be better in most circumstances than the current Shuriken catapult. The Shuriken Catapult should have stayed a semi-expensive upgrade, and lasguns should have continued in the basic Eldar lineup.

Yeeeaahh, I think they specifically didn't want lines of immobile Eldar, so just on principle I tend to prefer their general idea.

And that's how we ended up with Starcannon spam gunlines.

Wait...

Hellebore wrote:
the bolt shell casing is 20mm as well ( pictures design it that way) but I think there are a couple of hand waves for that one:

1) SciFi gunpowder requires less
2) it's only an initial propellant, so doesn't need a lot to get it going


A more interesting physics question for me, is the shuriken catapult. It's effectively a gravity wave powered coil gun. There are no physics I know of that will explain why the description of the weapon results in a 12" range...

I'm not sure if you mean "physics" or "existing sci fi setting that depicts them that way".

The physics is pretty easy. Low muzzle velocity, having a lightweight and/or high drag projectile, or poor accuracy will all result in a short maximum effective range of the weapon.

 Lord Damocles wrote:

 Insectum7 wrote:

 Elbows wrote:
Regardless of it's change...they were giving a Toughness 3 model with crap armour a 12" gun...as if they "wanted" to charge after using it. Eldar Guardians are as weak as guardsman when it comes to firepower. What they want is stand-off distance. They want a 24" gun. The old lasgun would be better in most circumstances than the current Shuriken catapult. The Shuriken Catapult should have stayed a semi-expensive upgrade, and lasguns should have continued in the basic Eldar lineup.

Yeeeaahh, I think they specifically didn't want lines of immobile Eldar, so just on principle I tend to prefer their general idea.

And that's how we ended up with Starcannon spam gunlines.

Wait...

People gonna do what people gonna do. Even so, that Starcannon could move and fire with the Heavy Weapon Platform. The Eldar weapons allowed them to keep up offensive output on the move. IMO great design.

 Inquisitor Lord Katherine wrote:

Hellebore wrote:
the bolt shell casing is 20mm as well ( pictures design it that way) but I think there are a couple of hand waves for that one:

1) SciFi gunpowder requires less
2) it's only an initial propellant, so doesn't need a lot to get it going


A more interesting physics question for me, is the shuriken catapult. It's effectively a gravity wave powered coil gun. There are no physics I know of that will explain why the description of the weapon results in a 12" range...

I'm not sure if you mean "physics" or "existing sci fi setting that depicts them that way".

The physics is pretty easy. Low muzzle velocity, having a lightweight and/or high drag projectile, or poor accuracy will all result in a short maximum effective range of the weapon.

Well the setting depicted then as superior storm bolters for two editions before beating them into the ground, so the game itself is an unreliable narrator (I think the assault cannon has had more versions than any other gun - 4-5 iirc).

My understanding of the physics you mentioned are limited so my assumptions are probably flawed. The gun fires very thin light weight discs. for it to be in any way accurate, wouldn't it need to necessarily fire them at high speed to reduce the effect of drag? Its depicted as being quite strong and penetrative, but that all comes from its speedv as it's a solid projectile.

It seems to me that you would have to go out of your way to design a gun to have just the right balance of poor designs to get it to be that bad...

EDIT: another way of saying this is:
It fires very thin flat discs that have very low mass, but hit with effective strength and penetration. As far as I can tell to get the latter from the former you have to fire it at very high speed.

And that requirement, also necessarily requires it have a longer range because speed is interchangeable in that equation for all aspects - penetration accuracy and range

VictorVonTzeentch wrote:

Charistoph wrote:

VictorVonTzeentch wrote:The weapon in these videos is a 20mm Rifled Grenade Launcher.

True. I was looking at more of a direct fire round than an AoE Weapon, as the Boltgun generally is not considered firing grenade equivalents.

Indeed, how ever the Inkunzi is a "Grenade Launcher" in thats just what its classified as. It fires more like a rifle, as it has a flatter arc and more velocity than a 30 or 40mm Grenade. Plus it has more than just HE. It has SAPHE, AP, HE.

But to put it in line with the current thought processes, the Boltgun is not considered a grenade launcher, but a rifle with explosive rounds. Explosives which are rather anemic when compared to what the equivalent grenade is in 40K.

Inquisitor Lord Katherine wrote:Sorry [a little bit], and was a little bit cranky that somebody felt the need to explain to me what a 40mm Bofors [and etc.] was. I despise it when people explain to me basic things that I already know.

I'm a tank & ship person [despite being an aerospace engineer], so I think of a 20mm gun as a very little gun.

To be fair, I agree with you that 20mm is tiny for modern tanks and has always been rather spare for ships.

The M4 Sherman was usually using a 75mm which makes the 20mm rather anemic, to say nothing of the 105 and 120s in current use. For ships, 20mm was usually the providence of anti-air fire, which have been largely ignored once guided missles and long bomb techniques which generally kept aircraft out of AAA range, and even the age of sail tended to go with a rather large bore. Which is why 20mm is usually only seen on aircraft these days, and why I automatically just associate it with aircraft rather than trying to put it on tanks or ships. This is more explaining my own thought processes more than anything.

Hellebore wrote:

 Inquisitor Lord Katherine wrote:

Hellebore wrote:
the bolt shell casing is 20mm as well ( pictures design it that way) but I think there are a couple of hand waves for that one:

1) SciFi gunpowder requires less
2) it's only an initial propellant, so doesn't need a lot to get it going


A more interesting physics question for me, is the shuriken catapult. It's effectively a gravity wave powered coil gun. There are no physics I know of that will explain why the description of the weapon results in a 12" range...

I'm not sure if you mean "physics" or "existing sci fi setting that depicts them that way".

The physics is pretty easy. Low muzzle velocity, having a lightweight and/or high drag projectile, or poor accuracy will all result in a short maximum effective range of the weapon.

Well the setting depicted then as superior storm bolters for two editions before beating them into the ground, so the game itself is an unreliable narrator (I think the assault cannon has had more versions than any other gun - 4-5 iirc).

My understanding of the physics you mentioned are limited so my assumptions are probably flawed. The gun fires very thin light weight discs. for it to be in any way accurate, wouldn't it need to necessarily fire them at high speed to reduce the effect of drag? Its depicted as being quite strong and penetrative, but that all comes from its speedv as it's a solid projectile.

It seems to me that you would have to go out of your way to design a gun to have just the right balance of poor designs to get it to be that bad...

EDIT: another way of saying this is:
It fires very thin flat discs that have very low mass, but hit with effective strength and penetration. As far as I can tell to get the latter from the former you have to fire it at very high speed.

And that requirement, also necessarily requires it have a longer range because speed is interchangeable in that equation for all aspects - penetration accuracy and range

So...

As you are probably aware, Energy = 1/2 *mv^2. Theoretically going faster is going to result in a more destructive weapon than being heavier, right? But no, because there's more at play in the flight of a shell, bullet, or tiny bladed disk.
Force = mass * change in velocity. This starts to show up part of the issue for faster lighter projectiles. If a fast, light projectile and a heavy, slow one experience the same force, in a given time, the lightweight one will experience greater change in velocity. But over that period of time, the faster projectile will also move farther, so even if it deviates or slows down more, it still went further in that time, so maybe it's still more accurate and lethal at a given range?

Well...

The two most important physical forces in governing how far a weapon can shoot are Drag and Gravity.
Near the surface of the Earth, Gravity can be generalized as a constant acceleration felt independent of mass. This favors going faster, since you'll travel further horizontally as you travel the same distance vertically.
Bullets and shells are supersonic and experience a lot of drag from a lot of different sources which requires a lot of calculus which I'm not even going to try to do without matlab or something. But in general, we'll say that Drag increases with the square of velocity, because simple aerodynamic drag is represented by 1/2*rho*A*Cd*v^2=D. This isn't actually accurate for a shell or bullet, because as you transition to supersonic speeds there's shockwaves and as you go really fast those will be more important, but the math only gets worse and the simple drag equation communicates the point: going faster = lots more drag.

Anyway, there's a sort of balance point where your shell has the right weight and velocity. If it's too slow, it won't go far enough before it hits the ground or has dropped too far to be used in direct fire engagements. If you trade too much weight for velocity, it will experience strong aerodynamic forces that will cause it to deviate quickly and slow down quickly losing the extra energy you gained from going fast to the air. Early subcaliber AT shells, like those of the 17pdr gun had can't-hit-the-broadside-of-a-barn problems partly for this reason. Note that the 77mm HV gun which used the same shell and architechture as the 17pdr but was shorter in barrel [and therefore slower] didn't have all the accuracy problems the 17pdr had. This was later rectified by designing better sabots and eventually just designing better guns and ammunition alltogether.

That balance point also changes drastically based on how you want the gun to perform. Early attempts with lightweight subcaliber munitions for capital warship guns had dismal results because of a variety of factors, including bad accuracy, materials exhibiting undesirable properties when striking armor leading to reduced effect of hits, and having a smaller bursting charge being less lethal overall to warships. Of course, a battle rifle and a 14" naval rifle are very different things so what matters to a naval rifle and how serious various forces are for it's shells may not be relevant to a shuricat.

Anyway, you want to go fast and be heavy. When in doubt, for an infantry-scale weapon, going fast is better than being heavy in theory, but there's a point where you go too fast for your geometry and material science and things stop working right.



Going back to the shuricat and away from 17pdr AT guns and 14" naval rifles, there are two other factors:
A thin bladed disk is not a good shape for a projectile from like any perspective. If it starts tumbling you're f***ed, and if it's spinning it will actually pull in a direction and not fly true.
Natural imperfections in the weapon will also make you inaccurate. If the projectile doesn't come out of the gun straight, then it won't go straight.


Automatically Appended Next Post:

 Charistoph wrote:

Inquisitor Lord Katherine wrote:Sorry [a little bit], and was a little bit cranky that somebody felt the need to explain to me what a 40mm Bofors [and etc.] was. I despise it when people explain to me basic things that I already know.

I'm a tank & ship person [despite being an aerospace engineer], so I think of a 20mm gun as a very little gun.

To be fair, I agree with you that 20mm is tiny for modern tanks and has always been rather spare for ships.

The M4 Sherman was usually using a 75mm which makes the 20mm rather anemic, to say nothing of the 105 and 120s in current use. For ships, 20mm was usually the providence of anti-air fire, which have been largely ignored once guided missles and long bomb techniques which generally kept aircraft out of AAA range, and even the age of sail tended to go with a rather large bore. Which is why 20mm is usually only seen on aircraft these days, and why I automatically just associate it with aircraft rather than trying to put it on tanks or ships. This is more explaining my own thought processes more than anything.

Even for ships, we were phasing it out by the end of WWII in favor of the 40mm's greater power.

 Inquisitor Lord Katherine wrote:

Hellebore wrote:

 Inquisitor Lord Katherine wrote:

Hellebore wrote:
the bolt shell casing is 20mm as well ( pictures design it that way) but I think there are a couple of hand waves for that one:

1) SciFi gunpowder requires less
2) it's only an initial propellant, so doesn't need a lot to get it going


A more interesting physics question for me, is the shuriken catapult. It's effectively a gravity wave powered coil gun. There are no physics I know of that will explain why the description of the weapon results in a 12" range...

I'm not sure if you mean "physics" or "existing sci fi setting that depicts them that way".

The physics is pretty easy. Low muzzle velocity, having a lightweight and/or high drag projectile, or poor accuracy will all result in a short maximum effective range of the weapon.

Well the setting depicted then as superior storm bolters for two editions before beating them into the ground, so the game itself is an unreliable narrator (I think the assault cannon has had more versions than any other gun - 4-5 iirc).

My understanding of the physics you mentioned are limited so my assumptions are probably flawed. The gun fires very thin light weight discs. for it to be in any way accurate, wouldn't it need to necessarily fire them at high speed to reduce the effect of drag? Its depicted as being quite strong and penetrative, but that all comes from its speedv as it's a solid projectile.

It seems to me that you would have to go out of your way to design a gun to have just the right balance of poor designs to get it to be that bad...

EDIT: another way of saying this is:
It fires very thin flat discs that have very low mass, but hit with effective strength and penetration. As far as I can tell to get the latter from the former you have to fire it at very high speed.

And that requirement, also necessarily requires it have a longer range because speed is interchangeable in that equation for all aspects - penetration accuracy and range

So...

As you are probably aware, Energy = 1/2 *mv^2. Theoretically going faster is going to result in a more destructive weapon than being heavier, right? But no, because there's more at play in the flight of a shell, bullet, or tiny bladed disk.
Force = mass * change in velocity. This starts to show up part of the issue for faster lighter projectiles. If a fast, light projectile and a heavy, slow one experience the same force, in a given time, the lightweight one will experience greater change in velocity. But over that period of time, the faster projectile will also move farther, so even if it deviates or slows down more, it still went further in that time, so maybe it's still more accurate and lethal at a given range?

Well...

The two most important physical forces in governing how far a weapon can shoot are Drag and Gravity.
Near the surface of the Earth, Gravity can be generalized as a constant acceleration felt independent of mass. This favors going faster, since you'll travel further horizontally as you travel the same distance vertically.
Bullets and shells are supersonic and experience a lot of drag from a lot of different sources which requires a lot of calculus which I'm not even going to try to do without matlab or something. But in general, we'll say that Drag increases with the square of velocity, because simple aerodynamic drag is represented by 1/2*rho*A*Cd*v^2=D. This isn't actually accurate for a shell or bullet, because as you transition to supersonic speeds there's shockwaves and as you go really fast those will be more important, but the math only gets worse and the simple drag equation communicates the point: going faster = lots more drag.

Anyway, there's a sort of balance point where your shell has the right weight and velocity. If it's too slow, it won't go far enough before it hits the ground or has dropped too far to be used in direct fire engagements. If you trade too much weight for velocity, it will experience strong aerodynamic forces that will cause it to deviate quickly and slow down quickly losing the extra energy you gained from going fast to the air. Early subcaliber AT shells, like those of the 17pdr gun had can't-hit-the-broadside-of-a-barn problems partly for this reason. Note that the 77mm HV gun which used the same shell and architechture as the 17pdr but was shorter in barrel [and therefore slower] didn't have all the accuracy problems the 17pdr had. This was later rectified by designing better sabots and eventually just designing better guns and ammunition alltogether.

That balance point also changes drastically based on how you want the gun to perform. Early attempts with lightweight subcaliber munitions for capital warship guns had dismal results because of a variety of factors, including bad accuracy, materials exhibiting undesirable properties when striking armor leading to reduced effect of hits, and having a smaller bursting charge being less lethal overall to warships. Of course, a battle rifle and a 14" naval rifle are very different things so what matters to a naval rifle and how serious various forces are for it's shells may not be relevant to a shuricat.

Anyway, you want to go fast and be heavy. When in doubt, for an infantry-scale weapon, going fast is better than being heavy in theory, but there's a point where you go too fast for your geometry and material science and things stop working right.

Going back to the shuricat and away from 17pdr AT guns and 14" naval rifles, there are two other factors:
A thin bladed disk is not a good shape for a projectile from like any perspective. If it starts tumbling you're f***ed, and if it's spinning it will actually pull in a direction and not fly true.
Natural imperfections in the weapon will also make you inaccurate. If the projectile doesn't come out of the gun straight, then it won't go straight.

Thanks for that breakdown, I didn't know drag increased with speed. This is why I find the physics around the catapult so interesting, nothing about it makes sense. Its firing mechanism is most closely aligned to a coil or rail gun (using gravity waves over electricity), but it fires something that no one fires today.

Based on design and description it:
Fires low mass thin flat discs ~20-30mm in diameter
It has a very high rate of fire
It is an accurate infantry weapon (it isn't a spray and pray weapon)

Id be making the numbers up, but I doubt the shuriken weigh more than a gram each (at the thickness indicated, the material would need to be denser than lead to have a higher mass).

Current descriptions state that the gravitic pulse it uses to fire the disc also shears it off a solid core of ammunition, which would itself require a substantial amount of force. One stick is good for hundreds of rounds, so maybe they're 300mm long and therefore the discs are ~1mm thick reach?

Isn't every bolter supposed to shoot self propelled miniature rockets? At which point why the feth do they have cases anyway? They should be like the alien marines rifle. Shooting caseless explosive tipped rounds.

Because cases keep your ammo from getting damaged. And for an initial charge you want that extra strength.

There is a reason caseless ammo was a failure in real life. It sux.

Hellebore wrote:


Thanks for that breakdown, I didn't know drag increased with speed. This is why I find the physics around the catapult so interesting, nothing about it makes sense. Its firing mechanism is most closely aligned to a coil or rail gun (using gravity waves over electricity), but it fires something that no one fires today.

Based on design and description it:
Fires low mass thin flat discs ~20-30mm in diameter
It has a very high rate of fire
It is an accurate infantry weapon (it isn't a spray and pray weapon)

Id be making the numbers up, but I doubt the shuriken weigh more than a gram each (at the thickness indicated, the material would need to be denser than lead to have a higher mass).

Current descriptions state that the gravitic pulse it uses to fire the disc also shears it off a solid core of ammunition, which would itself require a substantial amount of force. One stick is good for hundreds of rounds, so maybe they're 300mm long and therefore the discs are ~1mm thick reach?

Lexicanum states that it's an inaccurate weapon which is what limits it's effective range [IE: the range of 12" is the maximum range at which aimed fire expects to hit anything, not the range the gun can shoot]


Automatically Appended Next Post:

 Grey Templar wrote:
Because cases keep your ammo from getting damaged. And for an initial charge you want that extra strength.

There is a reason caseless ammo was a failure in real life. It sux.

Tank shells are caseless.

 Inquisitor Lord Katherine wrote:

 Grey Templar wrote:
Because cases keep your ammo from getting damaged. And for an initial charge you want that extra strength.

There is a reason caseless ammo was a failure in real life. It sux.

Tank shells are caseless.

True. But we're talking about small arms ammunition, not vehicle weaponry.

Caseless ammo for self-loading small arms sucks because its so fragile, and ammunition generally gets fairly beat up. Simply dropping a caseless round on the ground and getting a small dent in it can cause it to easily jam in the delicate loading mechanism that caseless ammo firearms have to have. A metal cased cartridge is significantly more durable, and because the loading mechanisms don't have to be gentle with the ammo even if the cartridge is damaged, with something like a small dent, they can usually function fine.

Caseless ammo also has a significantly lower shelf life because they aren't completely sealed from the humidity in the air. Over time, the powder will absorb humidity and become more inert. Metal casings are completely sealed off and, assuming no manufacturing defects, will remain viable indefinitely. Long term storage is a key benefit for military logistics. you don't want to have to constantly be throwing away your entire ammunition reserves because it becomes useless after 20 years.

The only real benefit to caseless ammo is that it is lighter and slightly cheaper in material costs(brass/steel casings are more expensive than a plastic tube). However these benefits don't outweigh the disadvantages. The US military's new 6.8mm round is still a cased cartridge, but they're replacing the brass casing with a polymer one that is lighter and cheaper. So they can have both of the benefits that caseless ammo offers without the downsides.

And when I say metal cartridges last indefinitely, I really do mean it. People are still occasionally using ammunition that was made during or before WW1 and it works just fine.

 Lance845 wrote:
Isn't every bolter supposed to shoot self propelled miniature rockets? At which point why the feth do they have cases anyway? They should be like the alien marines rifle. Shooting caseless explosive tipped rounds.

Apart from the other points raised already, bolter rounds have always been described as having a two-stage propellant. The case holds the initial charge that accelerates the bolt round out of the gun and then the self-propelled part takes over at some point after that.

A better question is why GW artists insist on having assault cannons spewing brass everywhere when that weapon has always been described as firing caseless ammo.

 Inquisitor Lord Katherine wrote:

Hellebore wrote:


Thanks for that breakdown, I didn't know drag increased with speed. This is why I find the physics around the catapult so interesting, nothing about it makes sense. Its firing mechanism is most closely aligned to a coil or rail gun (using gravity waves over electricity), but it fires something that no one fires today.

Based on design and description it:
Fires low mass thin flat discs ~20-30mm in diameter
It has a very high rate of fire
It is an accurate infantry weapon (it isn't a spray and pray weapon)

Id be making the numbers up, but I doubt the shuriken weigh more than a gram each (at the thickness indicated, the material would need to be denser than lead to have a higher mass).

Current descriptions state that the gravitic pulse it uses to fire the disc also shears it off a solid core of ammunition, which would itself require a substantial amount of force. One stick is good for hundreds of rounds, so maybe they're 300mm long and therefore the discs are ~1mm thick reach?

Lexicanum states that it's an inaccurate weapon which is what limits it's effective range [IE: the range of 12" is the maximum range at which aimed fire expects to hit anything, not the range the gun can shoot.

Lexicanum is quoting the 3rd ed codex and says that 'due to the lack of rifling in the barrel' it's inaccurate. Which is a nonsense statement in the same vein as 'due to the lack of rifling in the barrel buckshot is inaccurate'. Because Rifling isn't going to have any affect on a disc fired by a linear accelerator... That line disappeared in subsequent codices because it's ridiculous

Slipspace wrote:

 Lance845 wrote:
Isn't every bolter supposed to shoot self propelled miniature rockets? At which point why the feth do they have cases anyway? They should be like the alien marines rifle. Shooting caseless explosive tipped rounds.

Apart from the other points raised already, bolter rounds have always been described as having a two-stage propellant. The case holds the initial charge that accelerates the bolt round out of the gun and then the self-propelled part takes over at some point after that.

A better question is why GW artists insist on having assault cannons spewing brass everywhere when that weapon has always been described as firing caseless ammo.

I've never seen anything stating that assault cannons are caseless.

In 2nd ed, autoguns were caseless....

 AnomanderRake wrote:
Flashlight? Some kind of gas port? Gun camera?

I'm also curious as to why the iron sights are blocking the scope, but that's probably more to do with the iron sights being proportioned to show up in miniatures-game scale.

Closer look, the scope is offset to the left.

As for the main point, I always thought it was a multi-sensor combining laser, rangefinding, and optical cameras.

Slipspace wrote:
A better question is why GW artists insist on having assault cannons spewing brass everywhere when that weapon has always been described as firing caseless ammo.

Boltguns and Heavy Bolters, too, at one point.

Answer:

Hollywood, Rule of Cool, wins. Ejecting brass is more visually engaging, especially if you are going with just a still image.

If we're talking about multi-barrel rotary weapons...GW has gone off the deep end completely. The Terminator's assault cannon is a perfect example. You don't need a rotary weapon when you have maybe 200-300 rounds on board your squad's support weapon. You don't need a rotary weapon until you're stashing 2000-3000+ rounds and plan to go through it rather quickly. The majority of GW's rotary weapons are modeled with enough ammunition for around 2-3 seconds of firing...not even enough to heat up the barrels to require a rotary function. There's also no logic to the assault cannon and why it became Strength 6 with decent AP, when it should be a Strength 3, 8 shot assault weapon according to its looks/design.

Yeah, that's the problem with "rule of cool". For most weapon designs, that's "this looks/sounds cool" to someone who doesn't know anything about weapons, weapon design, or logistics.

25 years ago, things like "this gun shoots self-propelled explosive rounds" sounded like a sufficiently elaborate bit of hand waving to explain the bolter rifle being the biggest hand held gun in the game. And then they decided to add man-portable auto cannons.