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I'm wondering if anyone else absolutely hates the design ideologies that GW holds about tank armaments as much as I do.
I'm looking at the Vanquisher, the Baneblade, the Vindicator/demolisher demolisher cannons today.Of course, I'm not looking at the fantastical weapons, like the bright lance and lascannon because there, they have artistic license.

Now, for those who don't know, my qualm is the way GW makes use of barrel length. while a longer barrel can facilitate better long range shooting, it is only because it makes the shell more accurate because it gets more spin out of the rifled cannon, from what I've learned about tanks. But, at a certain length, a barrell becomes unusable because the cannon simply isn't long enough to fire the cannon accurately or without spurting flames everywhere. You can't even assume the cannons are situated further inside the tank because a. there isn't enough room for it in the demolisher LRMBT's turret, and B. it wouldn't be able to shift at all in a Vindicator, meaning its range of movement is minute. It's also worth noting the vindicator's demolisher shell (the one that comes with the kit) is as fething long as the entire demolisher cannon's barrel.

Whenever GW talks about the Vanquisher or the Baneblade's main cannon, they seem to be under the impression that the long length of the barrell lends massive force to the shot fired, but in fact, the opposite is true - the spin as the shell leaves the barrell would actually serve to siphon off energy and ensure that the round, while flying truer, would not hit as hard as if the barrel was short. It seems to me that if they want to express a powerful shell being fired, they should increase the radius of the gun, not the length.

I don't know in the end, this is me having a rant. I won't pretend I know nearly enough about the physics of barrel rifling and firing massive shells out of tiny cannons to say this is 100% true, but it is how I feel about the weapons we have in 40k.

The Demolisher cannon has a pretty short barrel and it's pretty strong. Weird how short it's range is, though.

Yeah, GW is really bad at designing tanks. Welcome to Warhammer 40,000, people make fun of Space Marines, Eldar are overpowered and you are a bad person if you bring in bigger models.

And that's why I proxied all my LR. For an army that it's based in WWI/WWII looks, I can't stand the looks of the ugly metal box with phallic guns that GW seems to think it's gothic . I like my tanks more streamlined, thanks.

M.

Hrm, no. Length and rifling have some correlation, but not in the way you think. Longer barrels will always (up to a point) generate higher velocities as the propellant is acting on the projectile for a longer period of time before dispersing than a shorter barrel.

One will notice that the Leopard 2 Main Battle Tank and M1 Abrams Main Battle Tank both have smoothbore guns, in fact largely the same gun, but the newest versions of the Leopard 2 now have a longer barrel than older versions to facilitate increased velocity (instead of upping to a 140mm gun) and thus have higher penetrative capability than older versions of the Leopard 2 and the M1 Abrams.

One can look at tanks through time and a similar trend. Look at the Panther's 75mm gun compared to a Sherman's 75mm gun and the Panther's barrel length is like twice as long and had way more penetrative capability and accuracy, and was in fact potentially going to be change to an even longer barrel. The Tiger likewise had a very long barrel relative to other tanks of its time, which (along with the relatively larger size of its projectile than most contemporaries and great optics) gave it incredible accuracy and range, while the Tiger II's gun barrel was even longer and resultingly more longer ranged and better penetrating.

 TheCustomLime wrote:
The Demolisher cannon has a pretty short barrel and it's pretty strong. Weird how short it's range is, though.

Yeah, GW is really bad at designing tanks. Welcome to Warhammer 40,000, people make fun of Space Marines, Eldar are overpowered and you are a bad person if you bring in bigger models.

I've always assumed the Demolisher cannon was akin to a kind of massive mortar more than a proper cannon.

 Vaktathi wrote:
Hrm, no. Length and rifling have some correlation, but not in the way you think. Longer barrels will always (up to a point) generate higher velocities as the propellant is acting on the projectile for a longer period of time before dispersing than a shorter barrel.

One will notice that the Leopard 2 Main Battle Tank and M1 Abrams Main Battle Tank both have smoothbore guns, in fact largely the same gun, but the newest versions of the Leopard 2 now have a longer barrel than older versions to facilitate increased velocity (instead of upping to a 140mm gun) and thus have higher penetrative capability than older versions of the Leopard 2 and the M1 Abrams.

I hadn't thought of that, actually. You're right. The longer barrel would mean the force built up by the explosion is focussed for longer. Does the Leopard then rely on the velocity of the projectile to make it fly true? I was under the impression that that would be wildly inaccurate.

 Scipio Africanus wrote:

 Vaktathi wrote:
Hrm, no. Length and rifling have some correlation, but not in the way you think. Longer barrels will always (up to a point) generate higher velocities as the propellant is acting on the projectile for a longer period of time before dispersing than a shorter barrel.

One will notice that the Leopard 2 Main Battle Tank and M1 Abrams Main Battle Tank both have smoothbore guns, in fact largely the same gun, but the newest versions of the Leopard 2 now have a longer barrel than older versions to facilitate increased velocity (instead of upping to a 140mm gun) and thus have higher penetrative capability than older versions of the Leopard 2 and the M1 Abrams.

I hadn't thought of that, actually. You're right. The longer barrel would mean the force built up by the explosion is focussed for longer. Does the Leopard then rely on the velocity of the projectile to make it fly true? I was under the impression that that would be wildly inaccurate.

The rounds are stabilized in flight by fins, they have a casing that makes them fit snug while shooting through the barrel that falls away and what actually hits the target is a 10kg hardened arrow that's roughly 31" long (often made from something like depleted uranium) travelling at ~1,700 meters/second.

Ammunition propellant is calibrated to the gun's length for maximum efficiency as well. If a gun has a shorter barrel, its propellant usually burns faster so that the thrust of the projectile isn't wasted when the round leaves the barrel. A slower burning propellant increases the burn time but allows for continuous acceleration along the length of a longer barrel.

However, if you put for example pistol ammunition in a rifle length gun you actually risk losing velocity due to friction from the barrel because the propellant is expended before the shell leaves the barrel, causing drag. Rifling is usually just enough to stabilize the round because too much spin also increases drag thus reducing range and penetrating capability.

actually, the OPs post shows how little about ballistics he understands. there are many variables that go into gun design. long barrels may impart more.power to a shell, but onpy to a certain length. some guns actually do have short fat barrels, like the 165mm demolition gun on the British AVRE.

but also remember, it's a game. since GW does so many things to piss everyone off, why not add one more, right?

I think the bigger question is why Lascannons have such long barrels. Light doesn't really need a barrel to focus it.

Well, this is a long discussion with a lot of things involved, but I'll try to keep it simple.

Generally (and I am ignoring things such as the vibrations forming in longer barrels during firing which need to be properly dampened), longer barrels guns on tanks are:

-More accurate (I stress generally)
-have a higher muzzle velocity (expanding gases act longer upon round)

These are great for anti-tank, or long distance applications. However at the same time:
-are heavier
-are unwieldy.

This means that it is difficult to field high calibre tank guns, purely because of the weight and the moment arms which can be placed upon the turrets. Furthermore, if you were to have a high velocity large calibre gun, you would place the barrel under enormous stress. Furthermore, the turret ring and turret would need reinforcing from the forces. As an example, the T-34-85 was attempted to be up-gunned to 100mm. The turret ring bent under a few shots. A heavy gun would also unbalance the tank as a firing platform.

Now lets look at some of the advantages of short barrel guns.

-Very easy to maneuver in urban environments
-Lighter, can be mounted on chassis which might not normally take guns that size.


If the demolisher cannon is an explosive round or chemical (it doesn't get's its power from kinetic energy) then there isn't much reason to mount a long barreled gun, especially if it lacks the propellant for long range engagements. Doing so could potentially overburden the tank or leave it unwieldy in urban settings.

 TheCustomLime wrote:
I think the bigger question is why Lascannons have such long barrels. Light doesn't really need a barrel to focus it.

Space magic.

 ClockworkZion wrote:
I've always assumed the Demolisher cannon was akin to a kind of massive mortar more than a proper cannon.

I assume that about most of the IG tank guns.

 TheCustomLime wrote:
I think the bigger question is why Lascannons have such long barrels. Light doesn't really need a barrel to focus it.

does it really matter? how do your lascannons fire?

 viewfinder wrote:

 TheCustomLime wrote:
I think the bigger question is why Lascannons have such long barrels. Light doesn't really need a barrel to focus it.

does it really matter? how do your lascannons fire?

Yes! In fact, it does! I could be doing my homework, learning a new language or enrich myself culturally. But no. I must debate the length of a fictional weapon as depicted on overpriced plastic models.

And my Lascannons fire sunshine and rainbows. For the Emperor.

 TheCustomLime wrote:

Yes! In fact, it does! I could be doing my homework, learning a new language or enrich myself culturally. But no. I must debate the length of a fictional weapon as depicted on overpriced plastic models.

And my Lascannons fire sunshine and rainbows. For the Emperor.

A man after my own heart.

I recently farted sunshine and rainbows. Glad to know that was, in fact, lascannon fire. Explains the hole in the chair.

I'm not going to nitpick the weapon designs too much because there's an important constraint on them: you have to be able to tell which gun is which from across the table. Realistic barrel sizes would all look the same and you'd have to keep asking which tank is which. As long as they don't look too obviously unrealistic that's a tradeoff I'm willing to make.

 TheCustomLime wrote:
I think the bigger question is why Lascannons have such long barrels. Light doesn't really need a barrel to focus it.

For the same reason that a telescope is a long cylinder: you need to place the lenses at a certain distance apart to focus correctly, and once you have a structure to hold the lenses you might as well enclose the whole thing and keep dirt off everything. In fact this would be extremely important for a lascannon, since dirt or scratches on the lens would reduce efficiency, and that lost energy has to go somewhere, which means excess heating. And when you're dealing with levels of power that can kill a tank even small percentage losses can quickly add up to turning your lascannon into a puddle of molten metal.

Kind of wish they actually understood how guns work.

 Peregrine wrote:
For the same reason that a telescope is a long cylinder: you need to place the lenses at a certain distance apart to focus correctly, and once you have a structure to hold the lenses you might as well enclose the whole thing and keep dirt off everything. In fact this would be extremely important for a lascannon, since dirt or scratches on the lens would reduce efficiency, and that lost energy has to go somewhere, which means excess heating. And when you're dealing with levels of power that can kill a tank even small percentage losses can quickly add up to turning your lascannon into a puddle of molten metal.

Why are you bringing real physics into this! Space battles have no room for logic!

kinda wish people got that this is a game... *sigh*

 Peregrine wrote:
I'm not going to nitpick the weapon designs too much because there's an important constraint on them: you have to be able to tell which gun is which from across the table. Realistic barrel sizes would all look the same and you'd have to keep asking which tank is which. As long as they don't look too obviously unrealistic that's a tradeoff I'm willing to make.

 TheCustomLime wrote:
I think the bigger question is why Lascannons have such long barrels. Light doesn't really need a barrel to focus it.

For the same reason that a telescope is a long cylinder: you need to place the lenses at a certain distance apart to focus correctly, and once you have a structure to hold the lenses you might as well enclose the whole thing and keep dirt off everything. In fact this would be extremely important for a lascannon, since dirt or scratches on the lens would reduce efficiency, and that lost energy has to go somewhere, which means excess heating. And when you're dealing with levels of power that can kill a tank even small percentage losses can quickly add up to turning your lascannon into a puddle of molten metal.

A Lascannon would need a barrel for proper focusing, yes, but not that long and thin. I would imagine a shorter, fatter barrel would be more suitable for focusing light for their purpose.

But I guess it would look pretty dumb.

 Scipio Africanus wrote:
I'm wondering if anyone else absolutely hates the design ideologies that GW holds about tank armaments as much as I do.
I'm looking at the Vanquisher, the Baneblade, the Vindicator/demolisher demolisher cannons today.Of course, I'm not looking at the fantastical weapons, like the bright lance and lascannon because there, they have artistic license.

Now, for those who don't know, my qualm is the way GW makes use of barrel length. while a longer barrel can facilitate better long range shooting, it is only because it makes the shell more accurate because it gets more spin out of the rifled cannon, from what I've learned about tanks. But, at a certain length, a barrell becomes unusable because the cannon simply isn't long enough to fire the cannon accurately or without spurting flames everywhere. You can't even assume the cannons are situated further inside the tank because a. there isn't enough room for it in the demolisher LRMBT's turret, and B. it wouldn't be able to shift at all in a Vindicator, meaning its range of movement is minute. It's also worth noting the vindicator's demolisher shell (the one that comes with the kit) is as fething long as the entire demolisher cannon's barrel.

Whenever GW talks about the Vanquisher or the Baneblade's main cannon, they seem to be under the impression that the long length of the barrell lends massive force to the shot fired, but in fact, the opposite is true - the spin as the shell leaves the barrell would actually serve to siphon off energy and ensure that the round, while flying truer, would not hit as hard as if the barrel was short. It seems to me that if they want to express a powerful shell being fired, they should increase the radius of the gun, not the length.

I don't know in the end, this is me having a rant. I won't pretend I know nearly enough about the physics of barrel rifling and firing massive shells out of tiny cannons to say this is 100% true, but it is how I feel about the weapons we have in 40k.

A longer barrel allows a Shell to more effectivly utilize the propellant, as long as the Shell is in the barrel its accelerating so a shorter barrel wastes the energy of the propellant.

Bishop F Gantry wrote:
A longer barrel allows a Shell to more effectivly utilize the propellant, as long as the Shell is in the barrel its accelerating so a shorter barrel wastes the energy of the propellant.

Only up to a certain point. The pressure of the gas behind the shell drops as the shell moves down the barrel, so at some point it drops low enough that the force it exerts on the shell is less than the friction between the shell and the barrel, and the shell will start to slow down. To take it to an absurd extreme, imagine a pistol bullet fired out of a mile-long barrel, it would come to a complete stop somewhere long before the end of the barrel.

Of course this all depends on the exact details of the gun, so it's impossible to say whether or not GW's barrel lengths are appropriate.

 viewfinder wrote:
kinda wish people got that this is a game... *sigh*

That doesn't excuse not knowing the basics of how guns work. It's a game, but things should still follow basic physics unless otherwise stated. If you don't it's just lazy or ignorant and throws the player out of the immersion.
It's like watching an action movie and the character uses the phone by lighting it with a fuze.

As GW makes no attempt to claim technical or mechanical realism is part of the game I do not hold them to that standard.

 Vaktathi wrote:
One can look at tanks through time and a similar trend. Look at the Panther's 75mm gun compared to a Sherman's 75mm gun and the Panther's barrel length is like twice as long and had way more penetrative capability and accuracy, and was in fact potentially going to be change to an even longer barrel.

They were both 75mm, but weren't they very different shell designs?

 TheCustomLime wrote:
I think the bigger question is why Lascannons have such long barrels. Light doesn't really need a barrel to focus it.

There are various physical considerations in the design of a laser tube. To make a generalisation it needs to be "long and thin" in order to properly generate and collimate the beam.

However, GW have never worried about realistic engineering to design the equipment in 40K. Many of the vehicles could not fit a crew or ammunition in the places they need to be.

AllSeeingSkink wrote:

 Vaktathi wrote:
One can look at tanks through time and a similar trend. Look at the Panther's 75mm gun compared to a Sherman's 75mm gun and the Panther's barrel length is like twice as long and had way more penetrative capability and accuracy, and was in fact potentially going to be change to an even longer barrel.

They were both 75mm, but weren't they very different shell designs?

During WW2 there were very few* all-rounder guns, if you wanted to blow stuff up with a high explosive round you generally needed a low velocity gun which meant a shorter barrel, whereas if you wanted to destroy a tank you generally had to smash a solid chunk of metal through it high velocity necessitating a longer barrel. The Panther was primarily a tank destroyer so mounted a long high velocity gun, the Sherman was intended primarily for blowing stuff up so initially mounted a low velocity 75mm gun which was notably shorter than the 76mm high velocity gun that the Sherman was eventually 'upgunned' to.

* even the dreaded Tiger supertanks were initially fielded with each tank paired off with a dinky little Panzer III retrofitted with the discarded short barreled low velocity guns removed from upgunned Panzer IV's, because the Tiger initially had no High Explosive ammunition.

 MWHistorian wrote:

 viewfinder wrote:
kinda wish people got that this is a game... *sigh*

That doesn't excuse not knowing the basics of how guns work. It's a game, but things should still follow basic physics unless otherwise stated. If you don't it's just lazy or ignorant and throws the player out of the immersion.
It's like watching an action movie and the character uses the phone by lighting it with a fuze.

not really... but ok, I guess everyone's gotta have a reason to whine about GW...