M-48's and other "very primitive" units in Battletech.

[Korzon77]

Because so far, even the most primitive age of war vehicles are fluffed as being equal to, or more likely somewhat in advance of our "modern" weapons, (as long as we accept the conceits of battletech). So if a rifle cannon is an example of how an M-1's 120mm looks in betch, how would you stat out the 90mm cannon of the M48?  What would it's armor be like in Btech terms?

[I am Belch II]

Sorry....but this topic again. It goes on....

Some people say that 120mm gun is a AC-2 at best. The armor is not as strong as battletech armor and stuff like that. But its a debate goes on, and on thru the years.

[Stormfury]

The approach from the writers has been "We're not saying that the Light Rifle Canon is equivalent to the 120mm Rheinmetall, but it's what we were looking at when we came up with the rules, and it weighs the same amount. Wink, wink, nudge nudge."

That being said, it looks like it has about half the velocity of the 120mm Rheinmetall. So aside from the mass and the range of it, probably something along the lines of an infantry Heavy Mortar. 220 kgs, base range 3, .34 damage, 4 kgs per shot.

Armour-wise, probably 3 or 4 points of BAR 2 per facing.

So, basically, target practice incapable of damaging a 'Mech. But maybe of some use against poorly-equipped infantry.

[Kit deSummersville]

The approach from the writers has been "We're not saying that the Light Rifle Canon is equivalent to the 120mm Rheinmetall, but it's what we were looking at when we came up with the rules, and it weighs the same amount. Wink, wink, nudge nudge."

No it's not. I didn't even know how much that real-life weapon weighed when coming up with the initial stats for the Light Rifle.

[Stormfury]

Cray's take on it was a little different. Herb's official position is that there is no relation between the weapons.

[Kit deSummersville]

Cray's take on it was a little different. Herb's official position is that there is no relation between the weapons.

Cray didn't propose the idea to Herb, he just submitted some writing for the equipment. Herb came up with the final stats.

[cray]

That being said, it looks like it has about half the velocity of the 120mm Rheinmetall.

How'd you reach that velocity value?

Cray's take on it was a little different. Herb's official position is that there is no relation between the weapons.

Cray didn't write the Rifle (Cannon) rules or fluff, though. ;)

Herb wrote them and is the line developer. If he says they're not modern tank cannons, then they're not.

However, my opinion is Rifle (Cannons) are a great fit to modern tank cannons for the following reasons:
1) Right timeline. Their date of introduction is "pre-spaceflight."
2) Right tech level. They're Tech B products.
3) Right fluff. They're fluffed as weapons hearkening to the 20th Century and available in rifle and smoothbore forms.
4) Right rules. Their inability to operate in space-to-space conditions is consistent with the (relatively) low velocity of modern tank weapons.

There are some differences from tank cannons - the lightest Rifle (Cannon) fires a 120lb shell - but they're definitely a much better match than autocannons, which are hyper-velocity products of the 23rd (and later) Centuries.

Cray didn't propose the idea to Herb, he just submitted some writing for the equipment. Herb came up with the final stats.

And he wrote the fluff, too.

[Kit deSummersville]

And he wrote the fluff, too.

Whoops! That was such a weird product to write for.

[Stormfury]

How'd you reach that velocity value?

Wikipedia.

Muzzle velocity for the M3 type thingy is 823 m/s (2,700 ft/s)

Muzzle velocity for the 120mm is 1,580 to 1,750 m/s (5,200 to 5,700 ft/s)

Not being a mathematician or engineer, "about half" is good enough for me :P

[rlbell]

Because so far, even the most primitive age of war vehicles are fluffed as being equal to, or more likely somewhat in advance of our "modern" weapons, (as long as we accept the conceits of battletech). So if a rifle cannon is an example of how an M-1's 120mm looks in betch, how would you stat out the 90mm cannon of the M48?  What would it's armor be like in Btech terms?

BTU weapons are governed by playability.  Real World weapons are governed by physics.  BT fluff is governed by writers' fiat.  If you go by the fluff, RW tanks and weapons blow chunks, and are not worth statting.  If you take the one hard number equating points of damage to joules of energy (each point of falling damage equates to 600 kilojoules), the BTU weapons suddenly seem rather lame, as the NATO L7 105mm/51 gun's 9 megajoules of muzzle energy would do a whopping 15 points of damage out to 100 hexes (which also implies that the M1 would shrug off gauss hits).  Unsurprisingly, using falling damage to convert weapon stats is decidedly unpopular.

[cray]

Wikipedia.

Muzzle velocity for the M3 type thingy is 823 m/s (2,700 ft/s)

Muzzle velocity for the 120mm is 1,580 to 1,750 m/s (5,200 to 5,700 ft/s)

Not being a mathematician or engineer, "about half" is good enough for me :P

I'm not seeing the connection. Why does an old, real world 90mm gun definitively mean that Rifle (Cannons) have such a low muzzle velocity when Rifle (Cannons) are fluffed as representing all manner of weapons? Note that "smoothbore" is an option called out in the same paragraph as their 20th Century origins.

BTU weapons are governed by playability.  Real World weapons are governed by physics.  BT fluff is governed by writers' fiat.  If you go by the fluff, RW tanks and weapons blow chunks, and are not worth statting.  If you take the one hard number equating points of damage to joules of energy (each point of falling damage equates to 600 kilojoules), the BTU weapons suddenly seem rather lame, as the NATO L7 105mm/51 gun's 9 megajoules of muzzle energy would do a whopping 15 points of damage out to 100 hexes (which also implies that the M1 would shrug off gauss hits).  Unsurprisingly, using falling damage to convert weapon stats is decidedly unpopular.

I don't agree with that conversion of damage for two reasons:

First, the response of armor to a low velocity, high-mass impact is not necessarily the same as its response to weapon damage. This is seen abundantly in real world armor. Example one: solid steel armor of WW2 tanks would laugh off a low-speed collision with a solid object (equivalent to a 'Mech's fall), but would part like butter for a shaped charge with far lower joules. Example two: Whipple shields would be crumbled and ruined by a low-speed collision with something massive (or even a kid's fist), but can stop high velocity space debris carrying megajoules of energy. Example three: the SAPI hard ceramic inserts used in US military body armor can crack from a drop to a squad room floor (20-40 Joules), but will stop an armor piercing 7.62mm rifle round (2200J muzzle energy.)

I mean, I've made carbon fiber-epoxy panels that withstand 9000-pound shock loading at about 30Gs, but I could also flex, crack, and break them with my spindly geek arms, which have not been sufficiently gamma-irradiated to match the Joule delivery of 135kg applied at 30Gs.

Therefore, just because the very thin 'Mech armor buckles and snaps because a 'Mech puts its weight on it is not indicative of the armor's response to ranged weapon attacks.

Second, a Gauss Rifle shell is a 125kg slug with a velocity sufficient to cross 360km in 60 seconds (and probably much less time). This sets a minimum of 6000m/s muzzle velocity and 150 megajoules per point of damage. Of course, with 60 seconds in flight the Gauss Rifle wouldn't achieve its noted aerospace hit rates - even JumpShips could dodge a shot - so you can figure the velocity is quite a bit higher. There are other possible means of evaluating Joules-per-point of damage: the novels LOVE to melt off armor with lasers (even though that's the least efficient means of damaging a target with laser energy) and you can ballpark the joules of energy by estimating the mass of armor changed to a molten state (steel and boron nitride both have known heat capacities). (I wouldn't use laser damage to estimate ballistic joules-per-point though; the energy transfer mechanisms are very different, as different as falling and cannon shells.)

Which ever you pick, the Joules-per-point of damage is a great deal higher for ranged weapons than falling.

[Kit deSummersville]

I'm not seeing the connection. Why does an old, real world 90mm gun definitively mean that Rifle (Cannons) have such a low muzzle velocity when Rifle (Cannons) are fluffed as representing all manner of weapons? Note that "smoothbore" is an option called out in the same paragraph as their 20th Century origins.

I believe the ill-defined "it" from this paragraph:

That being said, it looks like it has about half the velocity of the 120mm Rheinmetall. So aside from the mass and the range of it, probably something along the lines of an infantry Heavy Mortar. 220 kgs, base range 3, .34 damage, 4 kgs per shot.

refers to the 90mm canon, not a BT Rifle (Canon).

[Stormfury]

Yeah. I was saying that if a Light Rifle Canon was a reasonable (ish) match for the 120mm Rheinmetall, then the M3's damage-dealing ability against BAR 8+ armour was probably going to be about half that.

Or in this case, a weapon that will round down to zero damage against BT armour.

[Nebfer]

Well one thing is known if we assume that a "light" rifle is roughly equivalent to current day tank weapons, which runs a wide multitude of calibers from 100 to 125mm. Not all of them are going to be the same in capability, but due to the "low" resolution of the game they are all lumped into a single weapon system dealing "three" damage.

The only other thing known is that regardless of class they do not have the velocity to be effective at ranges greater than ~18,000 meters.

-----------------------------------------------
Battletech Gauss Rifles (and heavy's -the lights have no quotes) are consistently in the novels said to have a velocity that is hypersonic. At a minimum that's for a heavy 383 megajoules of Ke, incidentally that's a bit more Ke than the 16 inch L50 guns used on the Iowas (at the muzzle). A regular Gauss Rifle would have roughly 230 megajoules (if scaled from the Heavy).

Though their are thoughs who are insistent that mach 2 is the correct velocity and all others are bunk (including the space based calcs). This stems from the velocity given in the old yellow jacket fluff (it's also supposedly in one of the mercenary handbooks), as well as a few novels. Though these guys also use physics to say that hypersonic velocity for Gauss rifles is problematic due to momentum and what naught, a problem the Mach 2 numbers do not have. Though this is saying that roughly half a dozen quotes for mach two velocity's should be given higher weight of canonical fact than more than three dozen quotes indicating hypersonic... due to real life physics, something that B-tech already bends and brakes at points...

Though theirs another guy who complained that B-tech lasers can not be above a few gigajoules due to atmospheric interference and radiation issues, or something like that. Their for every time a author describes a laser as melting 500kg of armor he is lying and is in fact referring to explosively throwing chunks of armor off the unit with little in the way of melting (even if the author describes it as 500kgs of armor falling off bubbling to the ground). Never mind pulse lasers which can only cut never melt...


Though one issue for auto cannons (which AFAIK has roughly even numbers of quotes indicating supersonic as hyper velocity) is with the hyper velocity auto cannons, if regular guns are already this velocity whats the point of these ones? and why refer to them as such?

Though most of these guys take the novels and fluff to be higher canon than the games (rules).

[FedComGirl]

Tank cannons come in sizes smaller and larger than 100mm. The main sizes currently used are 105mm and 120mm but other cannon sizes are still used. Those canon sizes go back at least to WWII, which matches their pre-space introduction.

You really can't compare RL rifle cannons and BT autocannons. Well trained crews can fire rifle cannons at rates between 15-18 rounds per minute. An auto-loader can get up to 40. That's equal or better than any autocannon, at 2-3 rounds up to 7 shots per round. Aircraft cannons have even greater rates of fire. RL rifle cannons can also use a multitude of ammunition types.  BT rifle cannons can only fire 1 shot per round and can't use multiple ammo types.

Armor also isn't as weak as some say. If the threat to an Abrams is another 120mm cannon it's armor has to have a higher BAR. If you give the Abrams a light rifle cannon with BAR 4 armor all other tanks would also have light rifle cannons as there isn't anything smaller. Their armor would also be BAR 2-3. A space vehicle only needs 1 point of BAR 2 armor per location. I think pretty much any tank ever built has thicker armor than a lunar lander. Since BAR 4 armor is really light for a later 20th early 21st Century MBT the BAR would have to be higher. That naturally would increase the size of the cannon.

A 23mm Nudelman rapid-fire cannon was mounted on a space station although I think in BT terms it'd be classed as a support machine gun as it only weighs 39 kg.
Still if a machine gun with a muzzle velocity of 690 m/s (2,264 ft/s) can engage targets in space, a 120mm cannon with a muzzle velocity of 1,580 to 1,750 m/s (5,200 to 5,700 ft/s) should have no problem at all. Yet the rules say otherwise.

[Warclaw]

There are other possible means of evaluating Joules-per-point of damage: the novels LOVE to melt off armor with lasers (even though that's the least efficient means of damaging a target with laser energy) and you can ballpark the joules of energy by estimating the mass of armor changed to a molten state (steel and boron nitride both have known heat capacities). (I wouldn't use laser damage to estimate ballistic joules-per-point though; the energy transfer mechanisms are very different, as different as falling and cannon shells.)

Which ever you pick, the Joules-per-point of damage is a great deal higher for ranged weapons than falling.

Yeah, the thing is, the way the novels talk about how powerful mech-scale weapons are, I would EXPECT the damage at the point of impact to either be clouds of sublimated material heated almost to plasma state, or explosive spalling as the sudden heat differential within the armor plates caused rapid materiel expansion.  Melting?  NO, that's always struck me as somewhat...off.

[Nebfer]

The approach from the writers has been "We're not saying that the Light Rifle Canon is equivalent to the 120mm Rheinmetall, but it's what we were looking at when we came up with the rules, and it weighs the same amount. Wink, wink, nudge nudge."

That's basically what he told me.

Though at 55kg per shot it's shell is about the same weight of post ww2 120mm ammo, APCBC type ammo.

[FedComGirl]

I don't think you can really compare real world weights to battletech weights. They don't match up. You can't build real world vehicles in BT. Battletech weights are heavier.

[greatsarcasmo]

The Almaz gun was designed for self-protection. Against targets that would be more or less on a straight line vector and so close in velocity to the station as to make no difference. NOT an Aerospace fighter burning in at 3+Gs  from 3000 KM out. And maneuvering to boot. You can rig a crossbow on a satellite too, doesn't mean it is going to do squat...

A 23mm Nudelman rapid-fire cannon was mounted on a space station although I think in BT terms it'd be classed as a support machine gun as it only weighs 39 kg.
Still if a machine gun with a muzzle velocity of 690 m/s (2,264 ft/s) can engage targets in space, a 120mm cannon with a muzzle velocity of 1,580 to 1,750 m/s (5,200 to 5,700 ft/s) should have no problem at all. Yet the rules say otherwise.

[Nebfer]

I don't think you can really compare real world weights to battletech weights. They don't match up. You can't build real world vehicles in BT. Battletech weights are heavier.

I can make a reasonable M1 Abrams, sure the weights are off compared to the real ones but game wise it would work out, same over all mass, same speed (unless you want a Abrams with a disabled governor), with an analogous weapons load out to boot. Again while the weights do not match up, they don't necessarily have to, after all B-tech could be accounting for things we would not necessarily take into account. B-tech engines seem to be a lot more "modular", as in they can fit in just about any vehicle that it's compatible with, be it battlemech or conventional vehicle. Not to mention B-tech components seem to be built reasonably tougher than most real life weapons deal. Not to mention that they might be including items not typically listed as part of the engine, like say tracks or myomers.

In any case I can easily match up artillery guns with real life guns both with ammo weights and gun weights, well at lest two of them.
The Long tom at 30 metric tons and using 200kg of munition per shot easily match's up with a 240mm gun, like the US M1 240mm and the German 24cm H39, both weight around 30 metric tons (or close to it) and both guns fire 160kg shells (just add 40kg of propellent -which is close to what they used as well).

The Sniper at 20 metric tons and 100kgs of shot, corresponds well to the German 17cm K18, both are roughly in the same weight range, and shell (70kg projectile with 30kg of propellent) is close as well.

The 120mm gun on the Abrams may only weigh ~3200kg, but it's only a semi automatic gun firing rounds at 1,550 to ~1,750m/s (apx 12 megajoules at muzzle -8.5 in the Ke round). Now what would happened if we installed a auto loader to that, capable of loading a 3 to 10 round "clip" in under 5 seconds (and to say nothing of the feed system), upped the velocity of the projectiles by oh lets say ~50% (to say ~2,500m/s), requiring improved recoil gear. Added remote targeting systems as well as the ability to rotate left and right independently of the turret (say roughly 30 degrees either side), never mind increasing the elevation angles by twice as much as well (to over 50 degrees). Oh and the ability for the gun to be able to be reloaded at that angle as well. Add built in heat sinks and the connections to the "vehicles" system, also software and hardware to allow said weapon to be installed in most of the vehicles in your inventory with little modifications (I'd like to see a 120mm gun installed on a Bradly with no modifications to either object...). And perhaps some built in armor and durability.

Do you think you make a 120mm gun that dose all that in just four or five metric tons tons?
Sure for a 20 to 40mm auto canon-2, 7 tons might be a bit extreme but it's also factoring in that it's a generic system as well.

[cray]

I don't think you can really compare real world weights to battletech weights. They don't match up. You can't build real world vehicles in BT. Battletech weights are heavier.

They match up in select areas, so you can't issue blanket dismissals.

[FedComGirl]

The Almaz gun was designed for self-protection. Against targets that would be more or less on a straight line vector and so close in velocity to the station as to make no difference. NOT an Aerospace fighter burning in at 3+Gs  from 3000 KM out. And maneuvering to boot. You can rig a crossbow on a satellite too, doesn't mean it is going to do squat...

Machine guns can and are mounted on Aerospace Fighters. See the Dagger in Retrotech. Now if a machine gun with a muzzle velocity half that of a rifle cannon can be used in space, why can't the rifle cannon?

I can make a reasonable M1 Abrams, sure the weights are off compared to the real ones but game wise it would work out, same over all mass, same speed (unless you want a Abrams with a disabled governor), with an analogous weapons load out to boot. Again while the weights do not match up, they don't necessarily have to, after all B-tech could be accounting for things we would not necessarily take into account. B-tech engines seem to be a lot more "modular", as in they can fit in just about any vehicle that it's compatible with, be it battlemech or conventional vehicle. Not to mention B-tech components seem to be built reasonably tougher than most real life weapons deal. Not to mention that they might be including items not typically listed as part of the engine, like say tracks or myomers.

If the weights don't match up they don't match up. I also presume you used a light rifle cannon and BAR 4 armor or so. Try building a Sherman or an FT-17  under the rules and compare them for me please. And Tracks are part of the motive system and are factored in to the tanks weight.

The 120mm gun on the Abrams may only weigh ~3200kg, but it's only a semi automatic gun firing rounds at 1,550 to ~1,750m/s (apx 12 megajoules at muzzle -8.5 in the Ke round). Now what would happened if we installed a auto loader to that, capable of loading a 3 to 10 round "clip" in under 5 seconds (and to say nothing of the feed system), upped the velocity of the projectiles by oh lets say ~50% (to say ~2,500m/s), requiring improved recoil gear. Added remote targeting systems as well as the ability to rotate left and right independently of the turret (say roughly 30 degrees either side), never mind increasing the elevation angles by twice as much as well (to over 50 degrees). Oh and the ability for the gun to be able to be reloaded at that angle as well. Add built in heat sinks and the connections to the "vehicles" system, also software and hardware to allow said weapon to be installed in most of the vehicles in your inventory with little modifications (I'd like to see a 120mm gun installed on a Bradly with no modifications to either object...). And perhaps some built in armor and durability.

You wouldn't necessarily have to increase the weight. In fact autoloaders are meant to reduce weight. It also isn't much better than a good crew hand loading it. Vehicles also don't require heat sinks. And of course you're going to have to modify something to mount something bigger but it is possible. Sherman tanks for example went from a 75mm cannon to 105mms. Even the M1's cannon increased from 105mm to 120mm. A Bradly with a 120mm cannon would be interesting to see.

Do you think you make a 120mm gun that dose all that in just four or five metric tons tons?
Sure for a 20 to 40mm auto canon-2, 7 tons might be a bit extreme but it's also factoring in that it's a generic system as well.

The gun is just the barrel and mount. Not all that extra equipment you listed. They're also generic as well. Like autocannons rifle cannons would include various sizes in their classes.

They match up in select areas, so you can't issue blanket dismissals.

They don't match up all over the place. Those few places that do match up are the exceptions.

[Martius]

Machine guns can and are mounted on Aerospace Fighters. See the Dagger in Retrotech. Now if a machine gun with a muzzle velocity half that of a rifle cannon can be used in space, why can't the rifle cannon?

What is your source that a BT Machinegun has half the v0 of a BT light/medium/heavy rifle?

If the weights don't match up they don't match up. I also presume you used a light rifle cannon and BAR 4 armor or so. Try building a Sherman or an FT-17  under the rules and compare them for me please. And Tracks are part of the motive system and are factored in to the tanks weight.

The incarnations of those tanks in the BT universe follow those rules. Those in RL follow other rules of course. Different universe.

The gun is just the barrel and mount. Not all that extra equipment you listed. They're also generic as well. Like autocannons rifle cannons would include various sizes in their classes.

In BT a targeting computer consists of more than just a computer too....

They don't match up all over the place. Those few places that do match up are the exceptions.

Thats fine for me. The rules are given to construct units in the fictional universe of Battletech, not as guidelines for RL engineers. As such they have to bend to rules called 'game balance' instead of 'natural laws'. The moment those two match I look for a new game as I got plenty of RL anyway.  :D

[FedComGirl]

What is your source that a BT Machinegun has half the v0 of a BT light/medium/heavy rifle?

The v0s are for RL weapons, not fictional but it still makes one wonder. Why can't they operate in space?

The incarnations of those tanks in the BT universe follow those rules. Those in RL follow other rules of course. Different universe.

Very true. Some would have a Sherman be an equal to an Abrams. The FT-17 cannot be built at all.

In BT a targeting computer consists of more than just a computer too....

Yes some even have mechanisms that adjust the aims of the weapons they're attached to. How they can be pod mounted and easily installed and removed I have no idea.

Thats fine for me. The rules are given to construct units in the fictional universe of Battletech, not as guidelines for RL engineers. As such they have to bend to rules called 'game balance' instead of 'natural laws'. The moment those two match I look for a new game as I got plenty of RL anyway.  :D

:)

Which is why I originally said we shouldn't compare real life weapons to battletech ones.

I thought this was interesting. If I understand it right, the stats used to be official.

http://webspace.webring.com/people/uj/jymset/SD_Abrams.html

[Daemion]

The incarnations of those tanks in the BT universe follow those rules. Those in RL follow other rules of course. Different universe.

Not quite. Even if we hold to the qualifier 'BattleTech is the Future of the 1980s', The M1 was around in the 80s. That means it was also around in the '80s of BattleTech's Terra (Earth), and probably functioned in much the same way we recognize in our world now. So to with Shermans and any other historical weapon before that point in time.

It's when the Russians go to civil war that things diverge from our reality.

As it is, you cannot create an M1 or a Sherman in the current collection of BattleTech rules and expect them to operate as they should in what amounts as BattleTech's history (which at one point matches ours). To do so, you need a different set of rules to add on or supplement to reenact such historical fighting.

This may be something that could come out in a future product. We, the public, don't know. Until then, it's either up to us to be happy with what we got or come up with something that meshes well. (You can also borrow from other systems...  ;) )

The BAR system is fully inadequate to do the job, and it's already been stated that the guy who made the Rifle Cannons doesn't think of them as the real thing, only future analogs. Even if BAR is tweaked to get a different scale of effect to allow for it, we still need rules added to allow for primitive construction techniques which would allow for the ranges that the weapons in question are known to fight at.

I would love to see that in a rulebook!

Along with things like primitive infantry that don't have the gear/training/what-have-you that allows the elite units found in the BattleTech rules to run 11 kilometers an hour continuously and fire extremely accurately, while dodging and weaving to hopefully avoid any shot thrown at you by an advanced, near AI equivalent targeting system. (Seriously, where are the guys we're reading about in the novels?) The majority of your home militias, insurgencies, pirate bands, crime syndicates and general thugs are not going to be on that level, no matter how many laps they run a day or how many reps they can bench.

[Nebfer]

If the weights don't match up they don't match up. I also presume you used a light rifle cannon and BAR 4 armor or so. Try building a Sherman or an FT-17  under the rules and compare them for me please. And Tracks are part of the motive system and are factored in to the tanks weight.

Nope I used BAR 5 and for kicks an AC-2.

An FT-17 is probably a bit out of scope for B-tech rules, though it's possible to make a passable FT-17, Though the majority where armed with a MG, so a infantry MG would work fine. And I would doubt that the 37mm gun that some had would be best suited by the rifle cannon of B-tech, I also hesitate to use it for most early WW2 tank weapons as well. Most WW2 tanks are also not very well supported by the B-tech system.

The FT 17 would be a tank that moves 1 hex, mass's 7 tons and armed with a "portable" MG.
A Sherman would be a 33 ton tank that moves 4 hexes on roads and roughly 2 off road, with 2 "portable" MGs and a support MG. The gun is a bit harder, I do not think the Rifle cannons are appropriate here.

You wouldn't necessarily have to increase the weight. In fact autoloaders are meant to reduce weight. It also isn't much better than a good crew hand loading it. Vehicles also don't require heat sinks. And of course you're going to have to modify something to mount something bigger but it is possible. Sherman tanks for example went from a 75mm cannon to 105mms. Even the M1's cannon increased from 105mm to 120mm. A Bradly with a 120mm cannon would be interesting to see.

Autoloaders do not reduce weight, they only add weight. The weight savings are from the fact that the unit equipped with an autoloader can be made smaller (due to less crew) reducing the armor mass on the vehicle, but it would have to be made that way from the start. Dropping an autoloader in an Abrams would not result in it suddenly being a few tons lighter. It would in fact be a bit heavier, unless you made the turret a bit smaller.

And in B-tech you can swap out a weapons system from one unit and in just a few hours mount it on another unit with no noticeable modifications to any of the units and equipment involved.

The gun is just the barrel and mount. Not all that extra equipment you listed. They're also generic as well. Like autocannons rifle cannons would include various sizes in their classes.

Nice try you can not do it. You can not make a 120mm gun that can fire in rapid 3-10+ round bursts, and load another burst, fire projectiles at substantially higher MVs, have an independent traverse of the main turret, can elevate twice as high (or higher) as regular tank guns, as such has a high capability counter recoil system, can automatically reload it's rounds at any angle as well as including it's feed system, and has a built in heat sink system and connections for the unit wide system (modern naval guns that automatically fire rounds faster than 20 RPM are mostly water cooled), Not to mention the FC computers, diagnostic computers, EM Hardening, some light armor, has universal mounting hardware. And have a Gun and Mount only mass 4 metric tons. All these systems would be part of the weapons mount, if not where are they on the various B-tech units that have autocannons? The chassis? The engine? An autocannon is a complete independent weapons system, it has every thing it needs to function on it's mount. Many current real world naval guns are unmanned systems that mass in excess of 7 tons (5 inch guns are 20+ tons). In that 7 or so tons is the gun, it's mounting, it's ammo feed, traverse and elevation gear, recoil systems, aiming systems, various electrical systems, automatic reloading systems & it's ammo feed and a water coolant system for the gun.

Sure a Rifle cannon is generic, and includes calibers ranging from say 100 to 150mm, with heavier models having calibers in the 200mm range. So while a 120mm on the Abrams is not directly compatible to say the light rifle, it fits in it's bracket. The real question is do the rifle cannons in game truly fit into that time frame (i.e. are they current B-tech era weapons built to 20th century specs...) as has been suggested.

[FedComGirl]

Nope I used BAR 5 and for kicks an AC-2.

That's cool. Under armed but cool.

An FT-17 is probably a bit out of scope for B-tech rules, though it's possible to make a passable FT-17, Though the majority where armed with a MG, so a infantry MG would work fine. And I would doubt that the 37mm gun that some had would be best suited by the rifle cannon of B-tech, I also hesitate to use it for most early WW2 tank weapons as well. Most WW2 tanks are also not very well supported by the B-tech system.

The FT 17 would be a tank that moves 1 hex, mass's 7 tons and armed with a "portable" MG.
A Sherman would be a 33 ton tank that moves 4 hexes on roads and roughly 2 off road, with 2 "portable" MGs and a support MG. The gun is a bit harder, I do not think the Rifle cannons are appropriate here.

I'd use the light and medium rifle cannons for most WWI and WWII tanks, with the exception of the FT-17, which I haven't figured out how to build yet. The MG variant I can make a reasonable version but the cannon and other variants can't be done.

Infantry support weapons can't be mounted on vehicles over 4.999 tons and 3 MGs for a Sherman. I'd give the Sherman a medium rifle so it'd be more effective than WWI tanks but less so against modern ones. It also fits with the rifle cannons introduction dates.

Autoloaders do not reduce weight, they only add weight. The weight savings are from the fact that the unit equipped with an autoloader can be made smaller (due to less crew) reducing the armor mass on the vehicle, but it would have to be made that way from the start. Dropping an autoloader in an Abrams would not result in it suddenly being a few tons lighter. It would in fact be a bit heavier, unless you made the turret a bit smaller.

wiki says otherwise.
http://en.wikipedia.org/wiki/Autoloader  And no dropping an autoloader into an existing tank would not make it lighter. They're lighter when designed with an autoloader in place.

And in B-tech you can swap out a weapons system from one unit and in just a few hours mount it on another unit with no noticeable modifications to any of the units and equipment involved.

Are you talking about just replacing a damaged weapon? That can be done now. substituting other weapons though takes more effort. Just like it does now.

Nice try you can not do it. You can not make a 120mm gun that can fire in rapid 3-10+ round bursts, and load another burst, fire projectiles at substantially higher MVs, have an independent traverse of the main turret, can elevate twice as high (or higher) as regular tank guns, as such has a high capability counter recoil system, can automatically reload it's rounds at any angle as well as including it's feed system, and has a built in heat sink system and connections for the unit wide system (modern naval guns that automatically fire rounds faster than 20 RPM are mostly water cooled), Not to mention the FC computers, diagnostic computers, EM Hardening, some light armor, has universal mounting hardware. And have a Gun and Mount only mass 4 metric tons. All these systems would be part of the weapons mount, if not where are they on the various B-tech units that have autocannons? The chassis? The engine? An autocannon is a complete independent weapons system, it has every thing it needs to function on it's mount. Many current real world naval guns are unmanned systems that mass in excess of 7 tons (5 inch guns are 20+ tons). In that 7 or so tons is the gun, it's mounting, it's ammo feed, traverse and elevation gear, recoil systems, aiming systems, various electrical systems, automatic reloading systems & it's ammo feed and a water coolant system for the gun.

1) Battletech vehicles don't require heat sinks to fire rifle or autopcannons. It's a feature of their design. Mechs on the other hand do require heat sinks. If the heat sinks were part of the weapon they wouldn't generate heat.
2) 120mm cannons can be made to sustain that rate of fire and more. Read the article. It lists some that do far greater than that.
3) A good well trained crew can fire Well trained crews can fire rifle cannons at rates between 15-18 rounds per minute. Without autoloader.
4) All the other sensors and computers are part of other systems.

Sure a Rifle cannon is generic, and includes calibers ranging from say 100 to 150mm, with heavier models having calibers in the 200mm range. So while a 120mm on the Abrams is not directly compatible to say the light rifle, it fits in it's bracket. The real question is do the rifle cannons in game truly fit into that time frame (i.e. are they current B-tech era weapons built to 20th century specs...) as has been suggested.

Again there are cannon sizes smaller than 100mm. The Abram's 120mm cannon would be more of a Heavy Rifle not light.

Since they've been in production since their creation and I would have to say not. Besides why would they build them to lesser specs when they could build them to modern ones and not lose 3 points of damage?

[guardiandashi]

to be honest? I am going to throw in my 2cents and really tweek the arguement

the cannon on the modern abrams tank is NOT a heavy cannon, it is a primitive light or medium cannon that weighs closer to the amount that a heavy cannon weighs when you add in the support structures needed to make it work

the sherman example is most likely packing a slow firing (canon fire rate) machinegun (bigger round lower rof varient) that is primitive and thus runs up its mass into cannon ranges

the armor on WWI/II tanks is most likely primitive bar 1-3 armor varients IE more mass less points and the armor still suffers blowthrough crits like the low bar armor it is so ww2 sherman armor might be say bar2 armor that instaid of weighing 40kg/point weighs 100kg/point or more

[greatsarcasmo]

The aerospace rules are an abstraction. Therefore, they don't allow for Rifles. You want a rifle, file it under an autocannon. That is the best the rules are going to accommodate.  I'm sure, if, in universe, someone wanted to duct-tape a heavy cannon on a Corsair, nobody is going to stop them. You could even fire it. Hell, you might even hit something. Is it going to do damage? Who knows. Who cares. Put an AC/2 on it and call it done.

[Terminax]

It seems to me that trying to represent archaic units with the current rule set is somewhat pointless. Even if you simulate something with rules appropriate to your table, all you end up with something that cannot possibly be a challenge when playing.