36 replies to this topic

[SethAbercromby]

Alternative Title: 'Things you never needed to know'

So, BattleTech has a lot of stuff happening in it and there have been occasional disputes how much punishment a BattleMech can actually take were it to ever be confronted with modern weaponry. So I've taken the liberty of calculating the effectiveness of the armor using the BattleTech Machine Gun (for which I will be using BTMG as a shorthand) as reference and comparing it to the M2 Browning heavy machine gun, as for this I will assuming that the BTMG uses 12.5 mm anti-materiel ammunition.

First off, let's take the basic stats of the BT Machine Gun we'll be needing:
- 2 damage per turn
- 200 units of ammo per ton
- Each unit consists of x amount of rounds expended over 10 seconds

First, we have to specify the type of ammunition used for our calculation. For this I have decided to go with the M903 SLAP (Saboted Light Armor Penetrator) rounds as specified here. I chose them for being specifically designed to be used against light armored vehicles, attack helicopters and their high muzzle-velocity. The relevant data from the spreadsheet is as follows:
- Total weight: 94.99 g
- Projectile weight: 23.33 g
- Projectile velocity: 1,219.2 m/s

First we will need to determine how many rounds can be carried in one ton. For this we can simply convert 1 t into 1,000,000 g.

1,000,000 g / 94.99 g = 10,527.42

For the ease of the following calculations (and a speck of realism) I will round that number down to the next largest multiple of 200, where the lost weight can be attributed to ammunition belt and feeding mechanisms, which provides us with 10,400 rounds of ammunition.

From this we can determine the rate of fire by congratulating how many rounds are expended as part of one unit of ammunition over 10 seconds.

10,400 rounds / 200 units = 52 rounds/unit

Multiplying that value by 6 we get an effective rate of fire of 312 rounds per minute. This is a comparatively low rate of fire to the 450-600 rpm of an M2HB manned by infantry or mounted on armored vehicles, but this can have some practical reasons. Machine guns operating at a high rate of fire cause the barrel to become very hot which can lead to deformation. Mounted on a BattleMech, it is difficult to exchange the barrels quickly without the use of vulnerable mechanical equipment which through damage or inaccuracy could render the entire weapon ineffective or useless. A lower rate of fire significantly increases barrel life during sustained fire and may have been a deliberate design choice by manufacturers.

Moving on, we will need the kinetic energy delivered by a single round. With the documented weight and velocity of a M903 SLAP projectile we can calculate the potential energy in Joules.

Joules are calculated in weight in kg times velocity in m/s squared.

(94.99 g / 1000) * (1,219.2 m/s)² = 34,678.85 J

Knowing the energy of one projectile, we can calculate the energy of a full burst over 10 seconds.

34,678.85 J * 52 = 1,803,300.2 J

This is a good start, but we have nothing to compare it against yet. First, we will have to calculate the effective armor strength. In BT, armor is distributed in half ton packages consisting of 8 points each. From this we can determine the weight of one point of armor.

500 kg / 8 points = 62.5 kg/point

Since we now know the weight of each point and the energy of a BTMG burst, we can calculate how much energy it takes to penetrate a single kg of armor.

1,803,300.2 J / (62.5 kg * 2) = 14,426.4 J/kg

Using this knowledge we can figure out how much armor a different projectile could effectively penetrate, like a tank shell.

The Rheinmetall L55 of the Leopard 2 is used used on most current NATO main battle tanks under various names such as the M256 mounted on the M1A2 Abrahams. As projectile I will be using the DM53 120mm KE Projectile as documented here with the following specifications:
- Total Weight: 21.4kg
- Projectile weight: 8.35 kg (with sabot)
- Velocity: 1,750 m/s

Unfortunately it is very difficult to tell the weight of the sabot from a projectile, so for the sake of discussion, I will use the same weight ratio of the projectile to the total weight as the M903 SLAP. This will likely be rather inaccurate, but perhaps more truthful than including the entire weight of the sabot for calculating energy.

21.4 kg / (94.99 g / 23.33 g) = 5.26 kg

Using that weight, we can now determine the energy of the projectile. Using the same formula as above.

5.26 kg * (1,750 m/s)² = 16,108,750 J

From here we can see how much armor this projectile can penetrate through.

16,108,750 J / 14,426.4 J/kg = 1116.62 kg

And to compare in a more easily understood manner:

1116.62 kg / 62.5 kg/point = 17.87 points

For rate of fire, I couldn't seem to find documented estimates, so I'll use the 10 rounds per minute which have been common with previous-generation cannons. Skipping that calculation, 10 rounds per minute equate to 1,67 rounds per 10 seconds.

17.87 points * 1.67 rounds/turn = 29.84 points/turn

In other words, an L55 would equate to an AC30 with about 28 units of ammo per ton, but everything considered this is a quite formidable result for mechanics which were cooked up in the 80s.

I'd really love to know how exactly you can get a single M2HB to weight almost as much as a small car though.

Edited by SethAbercromby, 06 August 2016 - 05:52 AM.

[martian]

SethAbercromby, on 06 August 2016 - 01:17 AM, said:

...
In other words, an L55 would equate to an AC30 with about 46 units of ammo per ton, but everything considered this is a quite formidable result for mechanics which were cooked up in the 80s.

Sorry, but that's not correct.

Your Rheinmetall 120 mm L/55 cannon is equivalent of BattleTech Medium Rifle. So no AC30 with 46 reloads, but your L/55 would be doing mere 3 points of damage against typical BattleMech. And with six shots per ton of ammo.

For more details see Kestrel MBT.

Edited by martian, 06 August 2016 - 02:41 AM.

[SethAbercromby]

martian, on 06 August 2016 - 02:41 AM, said:

For more details see Kestrel MBT.

You can't exactly refute math with a 'nuh-uh'. If I made a mistake in my calculations I'm happy to concede, but this is just silly.

[martian]

SethAbercromby, on 06 August 2016 - 04:57 AM, said:

You can't exactly refute math with a 'nuh-uh'. If I made a mistake in my calculations I'm happy to concede, but this is just silly.

But I can and I do.

The Kestrel Main Battle Tank was armed with Heavy Rifle and it was among the best tanks of the early 24th century. It was armed with something similar to 20th century tank cannon, but the Kestrel's gun was more advanced and more poweful.

Your Rheinmetall (no matter L/44 or L/55) 120 mm cannon is 300 years older and more primitive. Therefore, I think that listing it as Medium Rifle is about right. Or perhaps it could be Light Rifle, doing no damage to standard BattleMech at all.

[SethAbercromby]

martian, on 06 August 2016 - 05:41 AM, said:

Or perhaps it could be Light Rifle, doing no damage to standard BattleMech at all.

The history of the BT universe has demonstrated several times that the tech-level tends to gravitate more around a WWII level with some shiny added toys as a legacy from eras they didn't blow up each other's research facilities. Regardless of that, I am not arguing the L55 as some tool from the actual universe, but to cross the gap between its fiction and our reality, seeing the practicalities when opposed to actual technology.

COmpletely unrelated to that, i corrected myself on the total ammunition capacity. I averaged out the damage for a per-turn basis but forgot to do the same for the ammunition it consumes. Averaging out the 46 actual rounds for 1.67 rounds consumed each turn we are left with 28 units of ammunition, which is still quite a lot.

[martian]

SethAbercromby, on 06 August 2016 - 06:02 AM, said:

The history of the BT universe has demonstrated several times that the tech-level tends to gravitate more around a WWII level with some shiny added toys as a legacy from eras they didn't blow up each other's research facilities. Regardless of that, I am not arguing the L55 as some tool from the actual universe, but to cross the gap between its fiction and our reality, seeing the practicalities when opposed to actual technology.

But you are not crossing the gap, on the contrary, your math goes directly against established "facts" of the BattleTech universe.

[Metus regem]

I'm going to side with Martian here, as there is a canonical UAC/20 that is listed at 203mm.... That being said most canonical AC/5's are listed between 90mm and 125mm, so it would stand to reason that the 120mm found on the Leopard II would be at best an AC/5.

Now when it comes to BT armour we know it is ablative, rather than traditional armour plates, so we do not know how strong it truly is.

[Zacharias McLeod]

martian, on 06 August 2016 - 02:41 AM, said:

Sorry, but that's not correct.

Your Rheinmetall 120 mm L/55 cannon is equivalent of BattleTech Medium Rifle. So no AC30 with 46 reloads, but your L/55 would be doing mere 3 points of damage against typical BattleMech. And with six shots per ton of ammo.

For more details see Kestrel MBT.

This is the best answer here.

Just look at the EX-TRO 1945 if you try to oppose real tank guns with the BT ACs.

The 8.8cm Gun (most terrific tank gun in WW2) is a big joke compare to an AC. Because the tanks in the EX-TRO 1945 use only BAR-5 Armor.

So so can not say the gun is caliber X so it must work like an AC/Y because the Y has the same size. This is totaly wrong.

[SethAbercromby]

Here's the thing about armor. Ablative is both better and worse than traditional armor plates. Ablative can take much worse initial hits at its best, but after that it gets a lot worse. That makes it very good for modern-day skirmishes but not so much for traditional extended combat scenarios like during WWII. To calculate that properly, you'd need some kind of armor expert, which I am not, so I have to use something more primitive as my baseline.

Anyway, here's the thing about weapons. Projectiles always begin as kinetic energy penetrators. You can take away from that by adding an explosive charge or other function for it to have a more specialized purpose, but BT lore as far as I am aware never goes out of its way to highlight default ammo as anything but traditional KEPs.

For a KEP, there are hundreds of factors that determine effectiveness. Shape of the head, density, deformation upon impact, but at its most basic it's a thing that goes really fast. The energy I calculated is what you can call the minimum base of effectiveness and I can't provide you with much more nuance than that.

For each weapon in BT, there is a set limit to the weight of a projectile so what we need is speed to determine its potential energy. To demonstrate why I have been reluctant to touch upon BT weaponry is simple, the math makes no sense when you put it against lore.

Let's take the AC/20. At 5 ammo per ton, each unit weights in at 200 kg. Before we even begin to unpack the logistics of loading single slug of that weight into a barrel, let alone firing it, let's just divide it into 10 more reasonably-sized 20 kg shells, around the weight of a 120mm grenade.

Unfortunately we don't have much to go by barrel length of the Autocannon, but it's reasonable to assume most Mechs won't lug around a several meters long tank barrel. The Barrel on the Atlas seems a good amount shorter than the L44 barrel, the shorter previous version to the L55, which otherwise remained largely unchanged. I'm digressing though. Using a rough estimate based on size with the Atlas being assumed at about 12 m height, the AC/20 on the Atlas seems to be somewhere between one half and a full meter, significantly shorter that modern cannons, but not unheard of during some periods of WWII like the PzKpfwI V's 75mm stub cannon designed to fire high-explosive shells at low velocities of 430 m/s. Here's our first bump though. While the Atlas's barrel is longer than that, it is still significantly shorter than traditional cannons which can get projectiles to a high enough velocity to become exceedingly effective as KEPs.

This would suggest that the AC/20 actually fires a series of high-explosive shells, which ablative armor would be quite effective at mitigating, but that's a can of worms I am not yet ready to open. So let's for the sake of discussion pretend the IS has developed a much more efficient propellant than can accelerate a projectile at several time more than what we are currently capable of without increasing handling risks to the point where the projectile exits the barrel at the same velocity as one fired from an L55 today.

For the weight of our projectiles, I'll use the same calculation as with the DM53 120mm KE Projectile.

20 kg / (94.99 g / 23.33 g) = 4.91 kg

4.91 kg * (1750 m/s)² = 15,036,875 J

15,036,875 J * 10 = 150,368,750 J

If we use that as our baseline for 20 points of damage, we can alter the calculation as follows

150,368,750 J / (62.5 kg * 20) = 120,295 J/kg

The new value for our armor has almost increased by a factor of 10. Let's see what that does for our machine gun.

Machine gun ammo is capped at 5 kg per unit of ammo. Let's stay with the spirit of a Machine Gun for anti-infantry purposes and use 50 rounds loaded into each unit, giving us an effective rate of fire of 300 rounds per minute, each weighting 100 g.

First, we will need to determine the amount of total energy we will need to deliver over 10 seconds and then for each individual round.

120,295 J/kg * (62.5 kg * 2) = 150,368,875 J

150,368,875 J / 50 = 300,737.5 J

I am now being lazy and will pretend as if the projectile being fired is exactly 25g. From this we can calculate the speed of our projectile.

sqrt(300,737.5 J / (25g / 1000)) = 3468.36 m/s

'sqrt' signifies that I am taking the square root of that answer. However, with that speed we are actually entering the realm of High-hypersonic speed exceeding Mach 10 (3,430 m/s). Outside of a Mech being effectively motionless against anything at that speed, a projectile would very likely glow hot and require extremely heat-resistant material, which would not fit with it being extremely cheap to obtain at 1,000 C-Bills per ton.

Who knows, perhaps the range of the MG is so short because ammo vaporizes before it has even cleared 100 meters, but I think that might've come up in the lore at some point.

Edited by SethAbercromby, 06 August 2016 - 11:58 AM.

[Metus regem]

Wrong, an AC/20 gets 5 "shots" per ton, that doesn't mean 5 shells. For example the Pontiac 100 found on the Victor battle Mech is a class 20 AC (AC/20), yet is stated to be 30mm, but fires 100 rounds per trigger pull. This is a weapon that gets 5 ammo cassettes per ton.

[SethAbercromby]

Metus regem, on 06 August 2016 - 12:29 PM, said:

Wrong, an AC/20 gets 5 "shots" per ton, that doesn't mean 5 shells. For example the Pontiac 100 found on the Victor battle Mech is a class 20 AC (AC/20), yet is stated to be 30mm, but fires 100 rounds per trigger pull. This is a weapon that gets 5 ammo cassettes per ton.

I have done that distinction several times for both ACs and the MGs, but there are some AC/20s in BT lore which do indeed load a full-sized 200 kg shell. If the only thing you can contribute to the discussion is pointing out me not explicitly stating that again for the AC/20, then I must have done everything else right.

PS:
The caliber of AC/20s is stated be everything between 25-203mm, ranging from equivalents to a large-caliber anti-aircraft gun up to a naval cannon.

Edited by SethAbercromby, 06 August 2016 - 12:43 PM.

[Zacharias McLeod]

From Sarna:
The Autocannon is a direct-fire ballistic weapon, firing HEAP (High-Explosive Armor-Piercing) rounds at targets either singly or in bursts.

So it is both armor piercing and high explosiv. And it is much better than normal ammunition. Todays ammunition would not make much damage against the modern armor used in BT.

A modern tank would have an armor of (lets say) BAR-8. And Mech armor ist BAR-10. And the tank guns would be more like the Heavy Rifle.

Just look at Sarna http://www.sarna.net/wiki/Heavy_Rifle.

And her is something about the BAR http://www.sarna.net...trialMech_Armor

Edited by Zacharias McLeod, 06 August 2016 - 12:52 PM.

[SethAbercromby]

HEAP is not a magic bullet. High-Explosive Anti Tank rounds use a highly pressurized jet of liquid metal that can penetrate steel by pressure alone, causing molten shrapnel to be blasted into the target. However, the higher the yield strength and heat resistance of a material is, the less effective HE ammunition becomes and there are various methods of protection that can mitigate the effect of a direct HEAT shell impact.

I decided to go with a KEP, because one you add explosive charges in a future setting with armor made of hundreds of unknowns, you might as well be drawing lots for effective strengths. KEPs have historically always been the armor-killers while HEs were designed to deal with everything that wasn't armored as well due to the much more significant internal damage HE can cause as long as it can get past the armor.

Edited by SethAbercromby, 06 August 2016 - 01:00 PM.

[martian]

SethAbercromby, on 06 August 2016 - 12:39 PM, said:

I have done that distinction several times for both ACs and the MGs, but there are some AC/20s in BT lore which do indeed load a full-sized 200 kg shell.

Can I ask you to list some examples?

SethAbercromby, on 06 August 2016 - 12:56 PM, said:

HEAP is not a magic bullet. High-Explosive Anti Tank rounds use a highly pressurized jet of liquid metal that can penetrate steel by pressure alone, causing molten shrapnel to be blasted into the target. However, the higher the yield strength and heat resistance of a material is, the less effective HE ammunition becomes and there are various methods of protection that can mitigate the effect of a direct HEAT shell impact.

You are confusing HEAT and HEAP ammo.

HEAT is the hollow charge ammo, while HEAP uses bursting charge.

SethAbercromby, on 06 August 2016 - 12:56 PM, said:

I decided to go with a KEP, because one you add explosive charges in a future setting with armor made of hundreds of unknowns, you might as well be drawing lots for effective strengths. KEPs have historically always been the armor-killers while HEs were designed to deal with everything that wasn't armored as well due to the much more significant internal damage HE can cause as long as it can get past the armor.

British Army has actually favored HESH ammo against armored targets such as tanks?

[SethAbercromby]

martian, on 06 August 2016 - 01:08 PM, said:

Can I ask you to list some examples?

I know they are there, but I cannot find any examples myself. I've heard the King Crab used to load these and was build in such a way to support it against the massive recoil, but I couldn't find much confirmation on that.

Quote

You are confusing HEAT and HEAP ammo.

HEAT is the hollow charge ammo, while HEAP uses bursting charge.

Having an explosive charge still decreases penetrative power. A wider head increases surface area and a hollow chamber filled with an explosive charge decreases tensile strength, so the projectile will deform more on impact. Depending on the material and construction, a bursting charge can theoretically penetrate more layers of armor, but hollow charges are very good at defeating single layers. Regardless however, if you want to defeat the best armor we currently have on modern tanks, neither will get you far.

Quote

British Army has actually favored HESH ammo against armored targets such as tanks?

And there is a reason they don't any more. HESH was a groundbreaking development at its time but it has long been replaced by KEPs as a dedicated armor-killer, with APFSDS leading the field for its much higher penetration factor. HESH is more effective with rifled tank guns like the British L30, but with smootbore cannons like the German L55 HEAT proved more efficient. Otherwise they fulfill the same purpose for each respective gun.

[Strum Wealh]

martian, on 06 August 2016 - 01:08 PM, said:

Can I ask you to list some examples?

Nebfer came up with a good list of examples (with sources!) a while ago.

Nebfer, on 08 August 2013 - 05:50 PM, said:

Parden the spelling, but this is from my raw files... (txt files)

 
 
================================
Machineguns
================================
20mm Gatling			  = 20mm (TRO 3039) skorpion tank entry
M100					  = 12.7mm (leithal hearitage) -Phawk
Johnston minigun		  = 20mm (temptation by war) Ranger VV1 -discribed as caseless (ch 14)
Scattergun				= 20mm (temptation by war) DI Schmitt
22mm Gatling			  = 22mm (TRO 3075) JES 1 entry
================================
Class 2 Autocannons
================================
Whirlwind-L			   = 32mm (Binding force) BlackJack BJ-1
Whirlwind-L			   = 30mm (Threads of ambition) Blackjack BJ-1
SarLon					= 30mm (TRO 3026) Warrior VTOL
Thor RAC-2				= 40mm (TRO 3058) Warrior VTOL
Mydron Model D-rf (Ultra) = 20mm (Imminent Crisis) Jagermech III  
Mydron Model D			= 30mm (Threads of ambition) Jagermech
Defiance Shredder LBX	 = 20mm (Fortress republic) -Catapult
================================
Class 5 Autocannons
================================
GM Nova 5  Ultra	  = 50mm (Binding force) -cataphract
GM Nova 5  Ultra	  = 40mm (Illusions of victory) -Cataphract
GM Whirlwind		  = 120mm (Thunder ridge & Wolves on the border) -Marauder
GM Whirlwind		  = 50mm (killing field) -Marauder
Armstrong J11		 = 80mm or 90mm (Thunder ridge) -Shawdow Hawk
Imperator-A		   = 80mm (Price of Glory) -Riflemen
Whirlwind			 = 60mm (Price of glory) -Wolverine
Whirlwind			 = 90mm (Wolves on the border) -Wolverine
Imperator Ultra AC-5  = 80mm (Storms of fate) -Vulcan & Daikyu
Armstrong AC-5		= 50mm (Double blind) -Clint
Armstrong AC-5		= 105mm (TRO 3075) -Merkava Hvy Tank
Pontiac Light		 = 40mm (Illusions of victory) -Striker mech
Snake killer LAC5	 = 60mm (Battlecorps) -Shadowhawk-9D
Mydron Model RC RAC5  = 50mm (A call to arms & fortress republic) -Legionnaire & Rifleman
Mydron Tornado  RAC5  = 50mm (By Temptations and By War) -DI Schmitt
Defiance type J AC-5  = 75mm (Heir to the dragon) -Zeus 6S
================================
Class 10 Autocannons
================================
Luxor-D				= 80mm (Price of glory, Ghost of winter) -Centuien
Mydron Excel UAC	   = 80mm (Patriots and tyrents) -Enforcer
Mydron Excel LBX	   = 80mm (Patriots and tyrents) -Dragon Fire
Mydron Excel LBX	   = 80mm (Illusions of victory)  -Cataphract
Defiance Disintegrator?= 100mm (end game) -Banshee
Mydron Model B		 = 80mm (Flash point) -Bushwacker
Federated AC-10		= 80mm (Flash point) -Enforcer
Imperator Code Red	 = 100mm (Flashpoint) -Challenger MBT
KaliYama			   = 80mm (Illusions of victory) -Orion
Imperator Code Red	 = 80mm (Illusions of victory) -Emperor
Imperator-B			= 80mm (Warrior en Guard) Urbanmech (implyed to be similer in caliber as the Riflemen)
================================
Class 20 Autocannons
================================
Death Giver				= 100mm (Heir to the dragon) -Atlas
Pontiac 100				= 100mm (Heir to the dragon) -Victor
Armstrong				  = 120mm (binding force) -Von Luckner MBT
Chemjet					= 185mm (TRO 3026) -Demolisher I tank
Crusher SH				 = 150mm (TRO 3026) -Hetzer Assault gun (or 120mm Threads of ambition)
Defiance Thunder Ultra	 = 120mm (Patriots and Tyrants) -Blitzkrig
Defiance Disintegrator LBX = 120mm (Patriots and Tyrants) -Barghest -Illusions of victory & The Dying time as well
Kali Yama Big Bore		 = 120mm (Threads of ambition) -Thunder
Tomodzuru				  = 180mm (Era Report 3052) -Hunchback
Luxuor Devastator		  = 120mm (Storms of fate) -Typhoon UAV
Death Giver				= 120mm (Storms of Fate) -King Crab

================================
Unknown type
================================
Jagermech "500mm" AC (Double blind) -most likely a typo
Mackie 5S AC-5 = 110mm (Birth of a King)
Jagermech 7F RAC-5 = 80mm
Templar omni, Grayson config AC-5 = 40mm (Imminent Crisis)
Blackjack omni LBX-10 = 80mm

Clan
Type 9 UAC 10 = 75mm
Type 10 UAC 20 = 120mm
Type 20 UAC 20 = 200mm
Type 25 UAC 2 = 50mm
Type 31 UAC 5 = 40mm
Type Kov LBX-10 = 75 or 150mm (same book two diffrent vehicles)
Type Covr-X 40mm

Wolves on the border LRMs = 75mm catapult ch 19
Gauss rifle = 10cm -starlord ch 2
infantry HMG "spanner" 15mm (not sure where this one is from)
Shrapnel mentions HE shells, a gray death book also mentions HE rounds...
blood legacy, unknown vtol, door mounted rotary 12.7mm MG
The Dying time, jeep mg = 13mm 43 gram -recount of thunder rift (1500 RPM)
temptation by war, ryoken II MGs = 20mm (likely AC-2s, as I do not think it has MGs)
patriots stand, generic gun trucks, 20mm "Gatling" MGs
flight of the falcon, mining mech mod, twin 50 cal MGs
Their are a few more but this is most of what I found, as one can see their is a few contradictions.

In general:
MGs = 12 to 20 mm
Class-2 ACs = 20 to 40 mm
Class-5 ACs = 40 to 120 mm
Class-10 ACs = 80 to 100 mm
Class-20 ACs = 100 to 185 mm
Gauss Rifles = 100 to 300 mm

With the ACs, one thing to consider is burst size: the Pontiac 100 on the Victor fires a burst of one-hundred 100mm shells to deal "20 units of damage", the Crusher Super Heavy Cannon on the Hetzer fires a burst of ten 150mm shells to deal "20 units of damage", and the ChemJet Guns on the Demolisher each fire a burst of four 185mm shells to deal "20 units of damage", but all are classified as "AC/20s".
By contrast, the GM Whirlwind on the Marauder fires a burst of three 120mm shells to deal "5 units of damage", and the SarLon Autocannon on the Warrior fires a burst of ten 30mm shells to deal "2 units of damage".

[martian]

SethAbercromby, on 06 August 2016 - 01:42 PM, said:

I know they are there, but I cannot find any examples myself. I've heard the King Crab used to load these and was build in such a way to support it against the massive recoil, but I couldn't find much confirmation on that.

So you said something what you can't prove ...

SethAbercromby, on 06 August 2016 - 01:42 PM, said:

Having an explosive charge still decreases penetrative power. A wider head increases surface area and a hollow chamber filled with an explosive charge decreases tensile strength, so the projectile will deform more on impact. Depending on the material and construction, a bursting charge can theoretically penetrate more layers of armor, but hollow charges are very good at defeating single layers. Regardless however, if you want to defeat the best armor we currently have on modern tanks, neither will get you far.

Unfortunately, we are not talking about armor of contemporary tanks, but about future BattleMechs. And the fact is that BattleTech Autocannons fire "high-explosive, armor-defeating shells". So your assumption "BT lore as far as I am aware never goes out of its way to highlight default ammo as anything but traditional KEPs." is invalid.

SethAbercromby, on 06 August 2016 - 01:42 PM, said:

And there is a reason they don't any more. HESH was a groundbreaking development at its time but it has long been replaced by KEPs as a dedicated armor-killer, with APFSDS leading the field for its much higher penetration factor. HESH is more effective with rifled tank guns like the British L30, but with smootbore cannons like the German L55 HEAT proved more efficient. Otherwise they fulfill the same purpose for each respective gun.

I listed it as example that you don't always need KEP do destroy armored target. So your assumption that "KEPs have historically always been the armor-killers while HEs were designed to deal with everything that wasn't armored" is not true, as you admitted.

--------------------------------------------------------------------------------------------------------------------

Plus, BattleMech armor is much more versatile than any tank armor we have today. It is also vastly more durable.

BattleMech armor must withstand kinetic damage (Gauss Rifle), combined kinetic/explosive damage (Autocannons), thermal damage (Lasers), combined thermal/kinetic damage (Particle Projector Cannons) and explosive damage (Missiles). And I am not even mentioning some more exotic weapons of BattleTech universe.

Your two generations obsolete L/55 tank cannon would be practically useless against extremely superior BattleMech armor.


Your basic error is that you are pretending that the contemporary Rheinmetall L/55 is more than BattleTech Light or Medium Rifle. It isn't, as I told you above.

1) BattleTech Autocannons are good for defeating BattleMech armor. This is the generation used in BattleTech universe "today".

2) Then you have the obsolete generation of Rifles that was almost useless against BattleMech armor (that was the Kestrel's main gun).

3) And before those Rifles was the generation of 20th century tank cannons - and "that" is your L/55. It would barely scratch armor of a modern BattleMech.

Edited by martian, 06 August 2016 - 10:45 PM.

[SethAbercromby]

martian, on 06 August 2016 - 10:39 PM, said:

So you said something what you can't prove ...

1) It is even mentioned on Sarna that single round AC/20s exist, just nobody actually made a proper list that can be shown to people or used for reference.
2) I could argue the same on your assumption of how powerful any AC type is. You have nothing to demonstrably prove the penetration factor of an HEAP.

Quote

Unfortunately, we are not talking about armor of contemporary tanks, but about future BattleMechs. And the fact is that BattleTech Autocannons fire "high-explosive, armor-defeating shells". So your assumption "BT lore as far as I am aware never goes out of its way to highlight default ammo as anything but traditional KEPs." is invalid.

Sure I made a mistake, but we're already past that. I see no reason to bring that up any more. My argument has simply changed to KEPs would make most sense to use.

Quote

I listed it as example that you don't always need KEP do destroy armored target. So your assumption that "KEPs have historically always been the armor-killers while HEs were designed to deal with everything that wasn't armored" is not true, as you admitted.

I didn't admit squat, you're just misconstruing my argument. First off, I said that it was made for targets that are not armored as well. HESH was designed to break bunker structures first and foremost but happened to be really good against tanks at its time because the armor was honestly quite terrible. Just adding a spall liner to the design however reduced the effectiveness of HESH significantly. Because of the modern history of combat being fought as skirmishes, increased protection against explosives like rocket launchers became paramount.

Ablative armor has by design a high heat resistance and can survive very hard impacts as they spread energy across their entire surface at the cost of a much higher rate of degradation, which would significantly reduce the effectiveness of any HE penetrator.

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Plus, BattleMech armor is much more versatile than any tank armor we have today. It is also vastly more durable.

BattleMech armor must withstand kinetic damage (Gauss Rifle), combined kinetic/explosive damage (Autocannons), thermal damage (Lasers), combined thermal/kinetic damage (Particle Projector Cannons) and explosive damage (Missiles). And I am not even mentioning some more exotic weapons of BattleTech universe.

Your two generations obsolete L/55 tank cannon would be practically useless against extremely superior BattleMech armor.

A PPC is more of a KEP. It functions like a Railgun accelerating super-heated plasma to a speed where the plasma punches through armor as if were a physical projectile, the heat radiating outward and causing additional internal damage.

That heat and explosive damage is largely ineffective against ablative armor is actually demonstrated in-universe, where missiles do only a single point damage to armor each. If HEAP was indeed the most efficient way to kill armor, a shaped missile warhead would be the most devastating Mech-killer we know of.

And I'm really not bothering to touch lasers. Beams are a terrible medium to transfer energy to anything and heat is very easy to defeat. Outside that we have no idea of the melting points of anything, a beam that can melt itself through several hundred kilograms of metal in just ten seconds would probably make the Mech firing it glow hot and likely melt all internals while it's at it.

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Your basic error is that you are pretending that the contemporary Rheinmetall L/55 is more than BattleTech Light or Medium Rifle. It isn't, as I told you above.

1) BattleTech Autocannons are good for defeating BattleMech armor. This is the generation used in BattleTech universe "today".

2) Then you have the obsolete generation of Rifles that was almost useless against BattleMech armor (that was the Kestrel's main gun).

3) And before those Rifles was the generation of 20th century tank cannons - and "that" is your L/55. It would barely scratch armor of a modern BattleMech.

For one, I'm doing this for fun and for the other I will still not simply accept an appeal to authority. There is no fun if we can't take a look at future stuff from a contemporary lens because 'muh future space magic'.

[martian]

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

1) It is even mentioned on Sarna that single round AC/20s exist, just nobody actually made a proper list that can be shown to people or used for reference.

Sorry, but Sarna is a fan-made page that every random visitor can edit.
Do you have a link to the page where it says that AC-20 fires one 200 kg projectile?

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

2) I could argue the same on your assumption of how powerful any AC type is. You have nothing to demonstrably prove the penetration factor of an HEAP.

I quoted what Battletech canon materials (TechManual in this case) say.

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

Sure I made a mistake, but we're already past that. I see no reason to bring that up any more. My argument has simply changed to KEPs would make most sense to use.

Unfortunately, that's not what BattleTech Autocannons use. Therefore, your conclusions have been based on incorrect assumptions. Sorry.

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

I didn't admit squat, you're just misconstruing my argument. First off, I said that it was made for targets that are not armored as well. HESH was designed to break bunker structures first and foremost but happened to be really good against tanks at its time because the armor was honestly quite terrible. Just adding a spall liner to the design however reduced the effectiveness of HESH significantly. Because of the modern history of combat being fought as skirmishes, increased protection against explosives like rocket launchers became paramount.

Ablative armor has by design a high heat resistance and can survive very hard impacts as they spread energy across their entire surface at the cost of a much higher rate of degradation, which would significantly reduce the effectiveness of any HE penetrator.

Still doesn't change the fact that BattleTech Autocannons do not fire KE penetrators such as that L/55 round that you linked above, but rounds with HE component. Sorry.

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

A PPC is more of a KEP. It functions like a Railgun accelerating super-heated plasma to a speed where the plasma punches through armor as if were a physical projectile, the heat radiating outward and causing additional internal damage.

Unfortunately, that's not how BattleTech PPCs work. They are explicitly described as "vaporizing tons of armor" (TechManual). Sorry, but you are wrong again.

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

That heat and explosive damage is largely ineffective against ablative armor is actually demonstrated in-universe, where missiles do only a single point damage to armor each. If HEAP was indeed the most efficient way to kill armor, a shaped missile warhead would be the most devastating Mech-killer we know of.

Seriously? If "heat damage is largely ineffective against ablative armor", why those MechWarriors bother with use their Lasers? You know, those weapons specifically described as "delivering concentrated heat" (TechManual)? One Heavy Large Laser can remove one ton of BattleMech armor in one shot.

And "That explosive damage is largely ineffective against ablative armor" is uncorrect too, as the example of the Arctic Wolf - specifically designed 'Mech only with missile armament - very clearly proves. (Technical Readout: 3060)

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

And I'm really not bothering to touch lasers. Beams are a terrible medium to transfer energy to anything and heat is very easy to defeat. Outside that we have no idea of the melting points of anything, a beam that can melt itself through several hundred kilograms of metal in just ten seconds would probably make the Mech firing it glow hot and likely melt all internals while it's at it.

Since Lasers have been used in BattleTech universe for centuries, obviously they are considered to be useful.

SethAbercromby, on 07 August 2016 - 12:18 AM, said:

For one, I'm doing this for fun and for the other I will still not simply accept an appeal to authority. There is no fun if we can't take a look at future stuff from a contemporary lens because 'muh future space magic'.

I am merely quoting canon BattleTech sources. You can ignore them, of course, but that doesn't change the fact that 20th century tank cannon is utterly obsolete in the official BattleTech universe. Naturally, in your fantasy world it can be different.

[Zacharias McLeod]

Someting about modern Laser Weapons.



And https://en.wikipedia...r_Weapon_System