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I'm just going to come out and say I think the leman russ is a bit of an abomination, but I think it suits the universe well enough, here are some thoughts about the tank that I think make sense.
The battle cannon is described as being an 120mm cannon, (or thereabouts on other patterns obviously there is a bit of leeway), I think this and the 'capable of 70kmph' is both part of the bit where they copied and pasted specs from the M1 Abrams page on Wikipedia.

Also has anyone actually read a story about a Russ going anywhere near 70kmph?

Anyway cynicism aside I can make a lot of sense from the gun is clearly not a very high velocity weapon, the fact the vanquisher exists explains such.
By battle cannon I can imagine something more along the lines of a low pressure gun, or failing that something as basic as a howitzer. The main role of the battle cannon is to put ordinance on target and a howitzer or low pressure gun is good enough for that, a projectile around the 120mm mark will obviously have considerable explosive payload(or any payload, this is the best thing about cannons, with the right ammo you can turn your tank into a giant self propelled shotgun, long range smoke marker etc), a HEAT round will deal well with armour with no regard to the projectile's own speed. In real life tanks are often used in indirect fire support, lobbing shells out to extended ranges sometimes out of LOS and I can imagine the regular leman russ battle tank doing this as well and the gun is large enough to be adequate for bombardment. I imagine the vanquisher cannon to be a higher velocity ~120 with a much longer propellant charge, the conqueror cannon a howitzer or low pressure gun in 90-100mm, with much less recoil compensating equipment(and much less recoil) meaning the vehicle is much lighter and this weapon is synonymous with the taurox prime gun. And i think all these ordinance guns have a fair bit of utility in the versatility of the rounds they carry and they could carry, hence a vanquisher is a more prized vehicle than say a leman russ annihilator.

The tank has a small footprint being short(in length(and therefore pretty poor in trench crossing)), and pretty narrow (with sponsons removed(no doubt a common practice for transport as was done historically)) sure it is tall, but it doe not occupy much floor space, which has to be important when you're trying to cram as many as you can into a transport ship. Also I can't help but think that a taller tank is going to fare better in a pushing contest against a large monster, and to stop enemy infantry(or human sized gribbles) from climbing aboard your own tank making it potentially better at withstanding melee combat than more sensibly designed tanks.

It's the quintessential Imperial tank. A poorly understood STC design that had some changes made to make it work and was then pressed into service because it was cheaper than the Malcador. Sometimes they're good and most of the time the crews die horrible deaths.

I think the actual model has a somewhat oversized gun in line with the general heroic weaponry proportions- that weapon is clearly bigger than ~5" diametre if scaled directly. I highly doubt anyone would claim 70mph these days, that appears to be an error. I could believe that as a top speed for a Hellhound or maybe a Chimera, but Russes are slower than both. Russes do appear to be capable of a fair turn of speed when needed, which I suppose could hit 70mph in ideal road conditions , and this is also reflected somewhat in the rules. It probably isn't a sustainable speed though.

I don't think the default battlecannon is low velocity (like, say, the short-barrelled 75mm on early Panzer IVs), but is a general purpose weapon with a reasonable velocity that can punch through the armour on light and medium vehicles (like the 75mm on the early Sherman). We know it can take out tanks reasonably well, and I don't get the impression it is just firing HEAT rounds from the FW information about Russ shells- they seemed to be AP capped shells.

Leman Russes absolutely do have multiple shell types available, and once upon a time had FW rules for several (mainly anti-tank and HE, but I think there were weirder options you could take like relics, such as phosphor shells). The big advantage of a Vanquisher is supposed to be that it can fire a normal battlecannon HE shell, but also high-velocity AP shells. Unfortunately, this ability was lost when the Vanquisher was added to the IG codex and the plastic kit released.

I don't think Leman Russes are bad at crossing trenches, the effective tread length is relatively long due to the sloped front of the tracks and looks enough to effectively cross the old FW Imperial trenchlines, for example. However, they do have the option for trench rails to assist with this, which is an easy fix.

Regarding its anti-tank capabilities, didn't the battle cannon have the Ordnance rule once upon a time? I recall weapons with that rule being relatively good at overcoming AV, so that would be a decent rules nod to the notion that they kill tanks reasonably well.

Wyldhunt wrote:
Regarding its anti-tank capabilities, didn't the battle cannon have the Ordnance rule once upon a time? I recall weapons with that rule being relatively good at overcoming AV, so that would be a decent rules nod to the notion that they kill tanks reasonably well.

It did.

In 4th, Ordnance weapons rolled on a better damage table.

In 5th, Ordnance rolled two dice for armour penetration, and picked the highest.

Even the 8th ed version has pretty good anti-tank capabilities.

Regarding the bore size of 120mm, IIRC it was determined years ago that this is the largest practical round size that a human loader can realistically handle and still maintain an acceptable rate of fire. Since the Russ has a human loader not an autoloader it makes sense. It just looks bad because GW weapons are heroic scale. A properly scaled 120mm barrel, even with a thermal sleeve or in the case of the Russ a water-jacket, would be about the diameter of a pencil. It would probably be more about the size of the GW autocannon.

But the most egregious problem for me is the complete lack of suspension. I would not like to ride in one over anything but a nice paved road.

 Haighus wrote:
Leman Russes absolutely do have multiple shell types available, and once upon a time had FW rules for several (mainly anti-tank and HE, but I think there were weirder options you could take like relics, such as phosphor shells). The big advantage of a Vanquisher is supposed to be that it can fire a normal battlecannon HE shell, but also high-velocity AP shells. Unfortunately, this ability was lost when the Vanquisher was added to the IG codex and the plastic kit released.

Beast Slayer shells were a thing from FW, I forgot if they were an upgrade for the Vanquisher or just built in back then, but they lost Armourbane in favor of getting Instant Death and a small blast profile (same AP/Strength).

Yeah if i recall correctly the vanquisher had all different types of shell. I have not heard the same for the battle cannon vehicle. The rounds generally attributed to the standard leman russ are a variety of APHE(what battleships used to fire), which makes no sense as the designation means it relies on kinetic force to penetrate. You would want to be firing that from a vanquisher(but a solid shot or HEAT round would work better). I have read that one of the vanquishers(the styrgies or ryza) fired a heat round so they have them in universe. There was also what seemed to be a hubrid HESH HEAT round for the conqueror, which was considered a failure(which makes a lot of sense), think it was a case of too many toaster collecting chefs ruining the AT broth. In modern tanks HEAT fills the role of a general purpose HE round, it makes the most sense for how the battle cannon behaves to me.

As for calibre the Flak40 128 in the jadgtiger was human loaded and a single piece shell. Obviously a 2 piece could be bigger and loaded easier but slower. And we see this in ww2 soviet vehicles. Sure it does not have the best reload times but that bigger blast would be useful., butfor a unitary cartridge for human loading122mm or 125 would be acceptable(as i said before i expect the classification battle cannon would be abything from 115mm-125 or maybe bigger.)

I do not mind the heioric scaling of the guns. It just means that no matter what happens to the vehicle your battle cannon probably will not break.

In one of the Imperial Armour books, I think Imperial Armour Volume 1 (second edition), there was an armoured battlegroup list.

It had the option (purely for lore) of allowing your Leman Russes to have two profiles, one for AP shells and one for HE. I think the HE shell was identical to the standard battle cannon profile of S8 AP3 large blast, but lost the "roll two dice, pick the highest" rule. I cannot remember the AP shell rule, butit was worse against infantry with better antitank in some way.

IIRC, it was something of a nerf in strict terms, but really cool. I think they rationalised the standard battle cannon profile as an average of the two for simplicity.

Yes, it's pretty obvious that the LRBT is armed with a low-velocity mortar (with the demolisher taking it to the extreme) rather than a true cannon. And it makes sense. When you have an abundance of accurate and powerful laser weapons that are perfect for killing armored point targets you have two uses for explosive weapons: engaging dispersed infantry and fortifications in direct fire support of friendly infantry, and offering a low-tech option for primitive worlds that lack the tech base to build the laser variants. A low-velocity mortar is perfect for both of those roles. It maximizes explosive payload against the targets that are best dealt with by blast waves, and the reduced barrel pressure is much more forgiving of poor quality metal than a high-velocity cannon. And while it's a weapon with poor accuracy and limited ability to defeat armor against enemy vehicles sheer explosive force does have a decent chance of getting a mission kill by blowing off a track, jamming a turret, etc, if the tank is forced to engage those targets without proper anti-tank support.


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Wyldhunt wrote:
Regarding its anti-tank capabilities, didn't the battle cannon have the Ordnance rule once upon a time? I recall weapons with that rule being relatively good at overcoming AV, so that would be a decent rules nod to the notion that they kill tanks reasonably well.

It did. Ordnance was roll 2d6 for armor penetration and take the highest value. But at S8 it was still fishing for 6s against AV14 targets and you only had a ~30% chance of a glancing hit. Seems about right fluff-wise though.

As mentioned above, the LRBT is a model that suffers from it's heroic proportions. A properly proportioned LRBT model would be a couple inches longer and maybe an inch wider, with the turret also being larger in all dimensions, with all of the weapons remaining the same size.It should really have about the same footprint as a land raider.

It should probably also have had 2 different ammo types. It is a decent representation of a simple high explosive shell which for tanks would be the most commonly useful shell. Modern tanks usually take 80% high explosive and only 20%ish armor piercing, but it should have had a single target armor piercing shell option as well as its high explosive round.

IIRC, the Ultramarine omnibus mentioned Lemun Russ's using APFSDS rounds against the Tau they were facing. Shredding right through the Hammerheads.

How is the battle cannon a low velocity mortar? It doesn't fire in a high elevation arc and clearly has a reasonable velocity more in line with a gun-howitzer as it has a very good range (obviously game ranges are an abstraction, but the battle cannon shoots 72" vs 48" for the heavy mortar, a similarly sized mortar weapon).

It is clearly more similar to infantry support guns like the Sherman 75mm that have a good HE round with ok AP capabilities when needed. The vanquisher cannon being the 76mm long barrelled equivalent.

The only kind of weapon referred to as a mortar with any similarities to Leman Russ weaponry is the petard on the Churchill AVRE, which has similarities to a demolisher cannon. This is described as a spigot mortar due to the weapon mechanics, but again does not get used as a mortar but instead as a direct-fire weapon. The demolisher is most likely not a spigot as it has a barrel, so does not share the one feature tying it to a mortar-like weapon. It does appear to be a low velocity weapon firing a huge shell, however.

 Haighus wrote:
How is the battle cannon a low velocity mortar? It doesn't fire in a high elevation arc and clearly has a reasonable velocity more in line with a gun-howitzer as it has a very good range (obviously game ranges are an abstraction, but the battle cannon shoots 72" vs 48" for the heavy mortar, a similarly sized mortar weapon).

It is clearly more similar to infantry support guns like the Sherman 75mm that have a good HE round with ok AP capabilities when needed. The vanquisher cannon being the 76mm long barrelled equivalent.

The only kind of weapon referred to as a mortar with any similarities to Leman Russ weaponry is the petard on the Churchill AVRE, which has similarities to a demolisher cannon. This is described as a spigot mortar due to the weapon mechanics, but again does not get used as a mortar but instead as a direct-fire weapon. The demolisher is most likely not a spigot as it has a barrel, so does not share the one feature tying it to a mortar-like weapon. It does appear to be a low velocity weapon firing a huge shell, however.

Here's a picture so that people know what the hell us WW2 tank fanatics are talking about. The US 75mm shell and 76mm shell as mentioned by Haighus.

And here is a 17 pdr shell for comparison.

Well the demolisher cannon could also be inspired by the sturmtiger's rocket mortar, as it was first mounted in the vindicator which pre dates the leman russ demolisher variant. It would then be natural to mount that gun in the tank's turret when all the russ variants started to come out.
The eradicator cannon could be argued as to be some kind of mortar, its large calibre, very close range(with a projectile of similar range of that seen with the demolisher mortar) and seems to rely on a very heavy ordinance, although what a sub atomic munition I do not know. Is it meant to be a small atomic munition or a shell the size of an electron. Not sure how that is supposed to kill infantry that are in cover.

I think what the Leman Russ is suffering from is unambitious lore. The battle cannon should be a 8" caliber monster and not a 120mm peashooter, and it should have a massive autoloader feeding the cannon from a gargantuan internal magazine. There should be no mechanical controls for the crew, but a Mind Impulse Unit interface they plug into. The turret should be unmanned and the crew compartment should be a tiny, cramped cockpit just enough for the crew to fit into physically. No safeties or comforts or anything, no escape hatches no nothing, and the only entry should be the shell ejection port on top of the turret - no moving around once the tank powers up, and if the tank dies the crew dies with it. Stuff like that. Sure, it would kill some memes and it would make the historic players seethe, but I don't really care.

Imperial Armour 1 book from FW says the Leman Russ has an on-road speed of 35 kph and off-road speed of 21 kph.

 OldMate wrote:
although what a sub atomic munition I do not know. Is it meant to be a small atomic munition or a shell the size of an electron. Not sure how that is supposed to kill infantry that are in cover.

A sub-atomic bomb was a theory originally proposed in the 1940s and used meson particles to make a extremely powerful device. It was more or less discredited and argued that it would be impossible to make. Apparently the Soviets during the 60s believed some CIA propaganda that the Americans already had them built. And then spent some years on fruitless research, despite several Soviet physicists saying it wasn't real.

Since then it's been a reasonably common sci fi trope to have sub atomic weapons and has been used often for 40k.

The idea that the Imperials are using this dangerous, virtually impossible weapon as fairly commonplace in their vehicles is sort of the theme of 40k.

 AtoMaki wrote:
I think what the Leman Russ is suffering from is unambitious lore. The battle cannon should be a 8" caliber monster and not a 120mm peashooter, and it should have a massive autoloader feeding the cannon from a gargantuan internal magazine. There should be no mechanical controls for the crew, but a Mind Impulse Unit interface they plug into. The turret should be unmanned and the crew compartment should be a tiny, cramped cockpit just enough for the crew to fit into physically. No safeties or comforts or anything, no escape hatches no nothing, and the only entry should be the shell ejection port on top of the turret - no moving around once the tank powers up, and if the tank dies the crew dies with it. Stuff like that. Sure, it would kill some memes and it would make the historic players seethe, but I don't really care.

I'd imagine you'd want some kind of drain hole/latrine hatch in the bottom as well. LOL

 Haighus wrote:
How is the battle cannon a low velocity mortar?

Because it's the only thing that makes sense unless you assume the model and art have nothing to do with the "real" tank. A tank that size isn't going to be able to mount a battleship-scale gun without being torn apart and flipped over by the recoil. And if you can't change the size of the projectile the only way to bring its momentum down to plausible levels is to greatly reduce its velocity. IOW, it's a massive projectile flung at low velocity over fairly short range, and with limited velocity it has to rely on sheer explosive payload to do damage. The demolisher cannon simply takes this to an extreme, adding even more payload at the expense of horrifyingly short range.

And, again, this makes perfect sense in a world where powerful laser weapons exist. When the LRBT's hull lascannon is a deadly tank killer (and not even close to the firepower of dedicated tank destroyers) you don't need a high-velocity gun. You just need something that can lob a bunch of explosives into a bunker or entrenched infantry. It's not like any of those targets are going to dodge and armor penetration is mostly irrelevant.

 OldMate wrote:

I'd imagine you'd want some kind of drain hole/latrine hatch in the bottom as well. LOL

gaking and pissing yourself is not an issue while submerged in a MIU interface so no, no latrine. I would say the rookies probably try to wear some kind of diaper, but the veterans just don't care and maybe even take special pride in sharing their body fluids with the machine in such an intimate way.

 Olthannon wrote:

 OldMate wrote:
although what a sub atomic munition I do not know. Is it meant to be a small atomic munition or a shell the size of an electron. Not sure how that is supposed to kill infantry that are in cover.

A sub-atomic bomb was a theory originally proposed in the 1940s and used meson particles to make a extremely powerful device. It was more or less discredited and argued that it would be impossible to make. Apparently the Soviets during the 60s believed some CIA propaganda that the Americans already had them built. And then spent some years on fruitless research, despite several Soviet physicists saying it wasn't real.

Since then it's been a reasonably common sci fi trope to have sub atomic weapons and has been used often for 40k.

The idea that the Imperials are using this dangerous, virtually impossible weapon as fairly commonplace in their vehicles is sort of the theme of 40k.

Sounds more like its just going to be another kind of 'turns anything it lands near inside out device.' So judging from the appearance of the weapon it is a kind of mortar that punts this sub atomic munition, which can't travel at high velocity as it maybe unstable?

CadianSgtBob wrote:

 Haighus wrote:
How is the battle cannon a low velocity mortar?

Because it's the only thing that makes sense unless you assume the model and art have nothing to do with the "real" tank. A tank that size isn't going to be able to mount a battleship-scale gun without being torn apart and flipped over by the recoil. And if you can't change the size of the projectile the only way to bring its momentum down to plausible levels is to greatly reduce its velocity. IOW, it's a massive projectile flung at low velocity over fairly short range, and with limited velocity it has to rely on sheer explosive payload to do damage. The demolisher cannon simply takes this to an extreme, adding even more payload at the expense of horrifyingly short range.

And, again, this makes perfect sense in a world where powerful laser weapons exist. When the LRBT's hull lascannon is a deadly tank killer (and not even close to the firepower of dedicated tank destroyers) you don't need a high-velocity gun. You just need something that can lob a bunch of explosives into a bunker or entrenched infantry. It's not like any of those targets are going to dodge and armor penetration is mostly irrelevant.

It just categorically is not a mortar though. It fires directly in a low angle of elevation.

I also fail to see how a weapon with such a long range can be low velocity. It has a considerably greater range than the hull lascannon, or the high velocity autocannon on SM Predators. It has a range equivalent to the very high velocity Hammerhead railgun. It is considerably longer ranged than the equivalently sized heavy mortar (...an actual mortar).

Sure, the weapon is comically big, but you just can't square that circle without either handwavium or artistic license. The weapon is treated as a tank cannon in the lore and rules, not a low velocity weapon and certainly not a mortar. It isn't high velocity either, with the Vanquisher specifically intended to fill that role, but somewhere in the middle.

Whilst I agree the battle cannon is not a mortar, I'd argue you can totally fire mortars at a flat trajectory, they just do not fly very far. which is totally okay if one wants to rumble up to a strong point and blow it apart/a hole in it.

the advantages obviously are that you can fire a massive shell. the other advantage is that as the projectile is flying slowly you can have a more flimsy and specialised munition.

A sturmtiger is a good example of a vehicle designed to rumble up to a target and blow it apart with its giant mortar. It can also lob the shells at a trajectory to a higher range, still only around 5km or so.

The vanquisher has longer range than that of the hammerhead last I checked. Makes sense to me, the hammerhead is relying on hyper velocity to puncture armour and probably for stability at standard combat ranges. A big ole heavy projectile is going to hold onto its momentum and carry its way through armour more easily.

 OldMate wrote:
Whilst I agree the battle cannon is not a mortar, I'd argue you can totally fire mortars at a flat trajectory, they just do not fly very far. which is totally okay if one wants to rumble up to a strong point and blow it apart/a hole in it.

the advantages obviously are that you can fire a massive shell. the other advantage is that as the projectile is flying slowly you can have a more flimsy and specialised munition.

A sturmtiger is a good example of a vehicle designed to rumble up to a target and blow it apart with its giant mortar. It can also lob the shells at a trajectory to a higher range, still only around 5km or so.

The vanquisher has longer range than that of the hammerhead last I checked. Makes sense to me, the hammerhead is relying on hyper velocity to puncture armour and probably for stability at standard combat ranges. A big ole heavy projectile is going to hold onto its momentum and carry its way through armour more easily.

I suppose it is fair to say that there are outlier weapons still called mortars like the Sturmtiger weapon, although I think most of these retain the name due to their lineage as heavy siege units. Generally speaking though, the defining trait of mortars is their arc of fire leading to plunging attacks. There are some gun-mortars which can lower to a gun level of elevation, but they are a hybrid class of weapon (hence gun-mortar).

I thought the GW vanquisher had range 72"? I think the FW vanquisher rules used to be 96" range.

 Haighus wrote:
It just categorically is not a mortar though. It fires directly in a low angle of elevation.

See OldMate's comment about short-range mortars on siege tanks.

I also fail to see how a weapon with such a long range can be low velocity. It has a considerably greater range than the hull lascannon, or the high velocity autocannon on SM Predators. It has a range equivalent to the very high velocity Hammerhead railgun. It is considerably longer ranged than the equivalently sized heavy mortar (...an actual mortar).

Because the LRBT's range isn't very impressive in the fluff. On the tabletop it has long range (though much less than proper long-range artillery) relative to other units but we know tabletop ranges are not to scale. If you assume its 72" tabletop range is to scale you get a fluff range of about 400', which is pathetic for a tank gun. And it's also silly that a tank gun that is a minimum of 120mm would have the same range as a Predator's 30-40mm autocannon. So either tabletop ranges are so hopelessly inconsistent that they add no value to the discussion or the LRBT carries a low-velocity mortar with incredibly short range for its caliber.

Sure, the weapon is comically big, but you just can't square that circle without either handwavium or artistic license. The weapon is treated as a tank cannon in the lore and rules, not a low velocity weapon and certainly not a mortar. It isn't high velocity either, with the Vanquisher specifically intended to fill that role, but somewhere in the middle.

How is it treated like a tank cannon in the rules? It's a blast weapon that does its damage through its explosive payload, not direct kinetic impact, and in previous editions it was worse than a lascannon at penetrating tank armor. You don't roll to hit with the direct shot, you lob a giant explosive shell into the general vicinity of the target and hope the AoE damage does enough to get a kill. And you don't even do so very accurately, as despite this massive explosive payload you can still miss entirely and shots with 1-2 hits are common.

CadianSgtBob wrote:

 Haighus wrote:
It just categorically is not a mortar though. It fires directly in a low angle of elevation.

See OldMate's comment about short-range mortars on siege tanks.

The exceptional examples that are not representative of the weapon type? The Sturmtiger weapon was called a mortar in German. I don't think the Churchill AVRE was officially armed with a mortar (I believe it was called a petard), mortar was only used to describe the spigot mechanism most commonly used for mortars (but also on the PIAT launcher, and no one is calling that a mortar).

I think those weapons are reasonable comparisons to demolisher cannons, and I can see a demolisher cannon being called a mortar, although I think cannon is still more appropriate (just a low velocity cannon).

I also fail to see how a weapon with such a long range can be low velocity. It has a considerably greater range than the hull lascannon, or the high velocity autocannon on SM Predators. It has a range equivalent to the very high velocity Hammerhead railgun. It is considerably longer ranged than the equivalently sized heavy mortar (...an actual mortar).

Because the LRBT's range isn't very impressive in the fluff. On the tabletop it has long range (though much less than proper long-range artillery) relative to other units but we know tabletop ranges are not to scale. If you assume its 72" tabletop range is to scale you get a fluff range of about 400', which is pathetic for a tank gun. And it's also silly that a tank gun that is a minimum of 120mm would have the same range as a Predator's 30-40mm autocannon. So either tabletop ranges are so hopelessly inconsistent that they add no value to the discussion or the LRBT carries a low-velocity mortar with incredibly short range for its caliber.

Obviously the tabletop ranges are not to scale, or the 5th edition version of the intercontinental ballistic deathstrike missile had a range of a mile...

However, they clearly give us range brackets. Most small arms are 12-24" with some stretching out to 30", support weapons like snipers or machine-gun equivalents (heavy stubbers, heavy bolters) usually reach out to 36". Most heavy weapons reach out to 48", incl. lascannons, autocannons, missile launchers, mortars. This is clearly meant to be pretty long-ranged weaponry. Anything beyond that is definitely long ranged, generally only the biggest guns have ranges beyond this.

I don't see why comparing to the autocannon is unhelpful? The battle cannon has a range 50% bigger on the tabletop, marking it out as significantly longer range. A demolisher cannon is shorter ranged whilst being an even higher calibre weapon, so clearly the autocannon does not do badly for range.

Also, what do you think has a longer range, the Churchill AVRE petard, the Sturmtiger mörser, or a Bofors 40mm...?

Sure, the weapon is comically big, but you just can't square that circle without either handwavium or artistic license. The weapon is treated as a tank cannon in the lore and rules, not a low velocity weapon and certainly not a mortar. It isn't high velocity either, with the Vanquisher specifically intended to fill that role, but somewhere in the middle.

How is it treated like a tank cannon in the rules? It's a blast weapon that does its damage through its explosive payload, not direct kinetic impact, and in previous editions it was worse than a lascannon at penetrating tank armor. You don't roll to hit with the direct shot, you lob a giant explosive shell into the general vicinity of the target and hope the AoE damage does enough to get a kill. And you don't even do so very accurately, as despite this massive explosive payload you can still miss entirely and shots with 1-2 hits are common.

It is a long-ranged direct fire weapon firing in a low arc, ergo a cannon. The fact it fires an explosive round doesn't stop it being a cannon... Tanks also mostly fire HE, and plenty of tank cannons were poor against armour (like the 105mm armed Shermans).

Also, whilst it is worse than a lascannon against enemy armour, it is better than an antitank missile... That feels like a damn effective weapon overall. As I said upthread, the battle cannon profile is an abstraction to simplify the game, and FW lore (and optional rules) split out the HE and AP rounds.

To me, the lascannon feels like a weapon like a 6pdr (57mm) gun, which was better at pentrating armour than the 75mm cannons on the Sherman or the Cromwell. However, the latter weapons were still cannon capable of punching through armour and had much more useful HE rounds. They were not low velocity, merely lower velocity than the 6pdr.

The LR battle cannon certainly looks to have an "equivalent" performance to a WWII asault gun... Like the 105mm Sherman or the Soviet SU-122... Big caliber guns mainly used for their HE capacity but with some secondary AT role.

Yeah that was my point originally lol, a howitzer or low pressure weapon would fulfill that task perfectly and you'd save room in ammo storage and recoil compensation equipment.
As for AT it mostly has to go up against vehicle wise, shabby ork scrap heaps, monsters and other imperial tanks. A HEAT or HEF round would work well in an AT role and both count on a large exsplosive payload, and work well even at a slower velocity.