Viability of Modernizing old Tanks?

[CaptHawkeye]

So I was doing a little reading on the T-55 and I was surprised to hear about how significant the upgrades were to the T-55AGM model. The AGM added important things that the T-55 had previously lacked like better gun stabilizing, infrared and night vision optics. Explosive reactive armour, the T-72's 2A46 gun, etc.

This modernization was surprisingly detailed and probably not a bad idea for a country like Ukraine, whose inventory of T-55s probably exceeds 50% of their force. But modernizations aren't cheap, in fact they're anything but as Skimmer always loves to point out. Just look at how ridiculously expensive the modernization of the old Standard Type battleships was.

But a battleship isn't a tank. So for one, is this sort of thing viable? Is it economic or would X country be better off just purchasing a fleet of modern MBTs? Also, what are the realistic expectations of vehicles like this against potential opponents?

At what point does one start "looking into" a modernization for a tank too? What would qualify a tank for a modernization vs. just building a new damn tank?

[Gunhead]

It depends what you want your tank to do. Modernizing is good when it's significantly cheaper than buying newer models and with the money invested you get improved performance against the threat facing you. Many countries don't have the necessary industry to produce a tank of their own, or it's too costly to do so, leaving them with buying one from someone else. Many T-55 refits have found a new lease of life as direct fire platforms used to beef up mech inf formations. It's a anti-tank gun / infantry support vehicle all wrapped in one. Other reason is the army's has a budget slot reserved for this year. You spend it now or it's gone. If the allocated money isn't enough to replace aging hardware, in large enough numbers, your only options are to upgrade existing vehicles or replace some vehicles now and hope you get more money before the new fangled hardware ages so much it needs to be retrofitted, leaving you with new and old vehicles in need of an upgrade.

-Gunhead

[Marcus Aurelius]

So I was doing a little reading on the T-55 and I was surprised to hear about how significant the upgrades were to the T-55AGM model. The AGM added important things that the T-55 had previously lacked like better gun stabilizing, infrared and night vision optics. Explosive reactive armour, the T-72's 2A46 gun, etc.

This modernization was surprisingly detailed and probably not a bad idea for a country like Ukraine, whose inventory of T-55s probably exceeds 50% of their force. But modernizations aren't cheap, in fact they're anything but as Skimmer always loves to point out. Just look at how ridiculously expensive the modernization of the old Standard Type battleships was.

I believe the T-55AGM was an export proposition. Ukraine has more T-64A/B and T-80UD tanks than they can use. They did modernize many of the T-64s to the T-64BU standard, but I don't think they have any plans to modernize their domestic T-55 forces. As far as I know there has been no buyers. The modernization is easily as expensive as buying a second-hand T-72M and giving it a fairly extensive modernization on top of that, so there is little sense in modernizing T-55s or even T-62s.

Modernizing tank makes sense only if A) it is domestically a more acceptable option than buying new tanks, B) you can't for some reason buy new tanks, so you have to modernize your old ones or C) modernizing the tanks make them reasonably competitive against your possible threat vehicles and is cheaper than buying new tanks or well-kept newer generation second hand tanks. The extensive modernizations for T-55 and T-62 are usually intended for cases A and B.

[Mr Bean]

Tanks like infantry weapons remain an area where it is quite possible small modernization efforts can pay off big dividends in making sure your 1960's era tanks are able to fight 1990's Abrams and it's modern counterparts. The concept of a tank remains the same since WWII. An armored vehicle that carries a powerful gun from which it can fire ammo to deal with both infantry and armor threats. The only things that have changed since WWII are a greater increase in the average speed of tanks, the amount of armor they carry, the size of the gun they field and the threat dimension of helicopters. A T-55 is already quite able to kill an Abrams for example but the Abrams can kill the T-55 from a greater distance frontally than the T-55 can. So upgrading the gun to give them the same kill ability with more modern ammo or a new turret helps a good deal.

Add in all the gadgets the Abrams has for making it easy to fire his cannon at a target at great distances while on the move and you have a good chance of hitting you. As well as the Abrams ability to fire blind again thanks to superior fire control. If you can upgrade your T-55's within spitting distance of that, there chances of surviving just went way up. This is one of the most expensive areas because T-55s were not designed with this kind of method of firing tanks in mind at the distances normally involved.

Make no mistake in Bocage style area a T-55 is well able to take an Abrams when your talking about 500 meter or less engagement ranges. However the Abrams can fight at 3,500 meters easily which the T-55 can't and off-setting that difference is where most of your costs are going to come in when upgrading as most countries with T-55's tend to have lots of Iraq style very open areas which play to all of the strength of modern tanks and let them dominate 60's era tanks.

[CaptHawkeye]

Hilariously a lot of people seem to think the only thing you need for a tank to be the biggest and baddest is the biggest gun and thickest armour. People really still think we build tanks based on archaic WW2-era design trends? It seemed pretty obvious to me that what makes a tank today is fire control, optics, and sensors. Situation awareness is more important than anything and all of the most ineffectual tanks in history tended to be weakest in that area.

Most of what makes modern tank guns more effective than older guns has more to do with ammunition quality than gun size. Armour effectiveness has a lot more to do with variety of defensive systems than just some big slab of face hardened unobtainium. It's all important stuff too, but Iraq made it pretty clear that if your tank can't shoot fast and shoot first, it ain't worth shit.

[Mr Bean]

Most of what makes modern tank guns more effective than older guns has more to do with ammunition quality than gun size. Armour effectiveness has a lot more to do with variety of defensive systems than just some big slab of face hardened unobtainium. It's all important stuff too, but Iraq made it pretty clear that if your tank can't shoot fast and shoot first, it ain't worth shit.

In Iraq which is ideal tank engagements conditions, nice wide open areas where cover only exists if you make it yourself or hide out in an urban setting. It's ideal tank country as long as you can control the air anyway. As was pointed out by Sea Skimmer in another thread awhile back, you can in American buy a WWII vintage M3 90mm AT/AA gun along with the ammunition for said gun and legally own said gun an ammunition. And said gun can mission kill an Abrams. Not at the 3,500 meters an Abrams can engage a static gun like that but 500 meters or less the 90mm will ruin his day.

If your country is not composed of giant open spaces or you don't fight tank to tank in giant open spaces then most of the advantages of a 21st century tank go away and a T-55 can engage an Abrams tank to tank and win. Crew skill becoming a much bigger factor than excellent optics and fire control software. That's my point CaptHawkeye. You can swap out Abrams for a Challenger, an Leopard or take your pick of high end tanks and the same facts hold true.

An WWII Cruiser Mk VIII Challenger and a modern Challenger II are very different tanks but the idea of "tank" remains the same between them. That of a heavily armored mobile platform with a turret and a gun capable of defeating any armored threat it can run across. The Challenger 2 throws on bonus features like the mentioned optics, a rifled barrel, a much greater range. Better handling, better acceleration/deceleration and and more. However while the number of special rounds has expanded since 1945 in addition to threats the idea remains the same.

[Marcus Aurelius]

A T-55 is already quite able to kill an Abrams for example but the Abrams can kill the T-55 from a greater distance frontally than the T-55 can. So upgrading the gun to give them the same kill ability with more modern ammo or a new turret helps a good deal.

Make no mistake in Bocage style area a T-55 is well able to take an Abrams when your talking about 500 meter or less engagement ranges. However the Abrams can fight at 3,500 meters easily which the T-55 can't and off-setting that difference is where most of your costs are going to come in when upgrading as most countries with T-55's tend to have lots of Iraq style very open areas which play to all of the strength of modern tanks and let them dominate 60's era tanks.

Let's put it this way. A T-55 can certainly kill an M1A2 Abrams, but for anything else than a mobility kill you will already need modern APFSDS ammunition or get to fire from behind. There actually in no known 100 mm ammo that would go through the frontal armor of the M1A2, either. So you need to upgrade the gun, but the T-55 turret is already cramped, so upgrading it to 120 mm or 125 mm makes the original seem roomy. Then you cram in all the FCS and night vision improvements as well, which you will need anyways (they are the first thing any sensible upgrade includes like CaptHawkeye implied) . If you want better mobility you will need a more powerful engine and possibly updated suspension, and even upgraded armor won't stop a modern 120 mm APFSDS.

So you pay a shitload of money and get an extremely cramped vehicle that is about as capable as a T-72M1 with just an ammo, FCS and night vision upgrade. If the T-72 gets an armor upgrade as well, it will be better than your super-T-55 can ever be. This is the reason why modernizing anything older than a T-72 or M60A1 does not make much sense from a technical point of view. Politics are of course a different matter, like I wrote in my earlier post. Or if you need just a fire support vehicle for counter insurgency, you can make do with just armor and possibly night vision upgrade and you are good to go, but then we are not talking about classic armored combat.

[Sea Skimmer]

Some really elaborate upgrade programs for the T-55, T-62, M48 and M60 series tanks exist but very few have been produced because the mass second line divisions they were expected to equip until roughly 1994 simply don’t exist anymore. Additionally and importantly, the huge stocks of reserve ammunition the world built up to fire out of those gun barrels is time expiring and much has already been disposed off. Buying a few new armor piercing shells for obsolete guns isn’t such a bad deal, but when you need to get it all new then who are you really kidding on saving money?

Instead all those obsolete tanks are being scrapped or on the surplus market or even being given away for the cost of delivery, meaning that everyone can shop around. Often you could just get a better version of the same crappy tank rather then upgrade your own existing model. As has been recently shown, even a place like African like South Sudan can scrap together money to import used T-72 tanks and just about any major power will opt new. Even in places like Israel and Turkey and South Korea which still do have major mobilization reserves to equip, as well as having actual money to spend, still emphasis new production over upgrades. Upgrades have a place but it is fading quickly, the concept was far more sound in the 1990s and a lot of what you see advertised is leftovers from that time.

World tank fleets got massive in the cold war because the only thing that could oppose a large mass of tanks was another large mass of tanks, major terrain obstructions, or else nuclear weapons employed both to destroy tanks and make rather massive road craters. Now anti tank missile, artillery and air to ground technology has all improved to the point that masses of tanks can be somewhat reliably broken up by lighter forces at long range.

The result is tank fleets shrink back down to a role directly proportional to supporting the infantry. That means divisions with two or three tank battalions instead of six or seven, but supported by ever more heavily armed infantry carriers and infantrymen. Extremely advanced active protection systems combined with unmanned ground vehicles (imagine a tank that drops dozens of robots with machine pistols) may reverse this trend and renew the independent power of the tank, but that’s a consideration for the next decade of budget planning, not what anyone is doing right now.

Ukraine is a pretty well perfect example of too many tanks to count. It inherited the equipment of around forty fully mechanized Soviet divisions, though not all of them were at full strength. Still it’s something like 7,000 tanks. This is close to as many tanks as Iraq and the Coalition fielded in the Gulf War combine.

Now as far as insane upgrades go... if you want to spend the money the T-55MV6 looks good. It modestly upgrades your T-55 by cutting it in half and making it longer to hold a sixth road wheel, the result being your T-55 can now mount a complete turret from the T-72B which has been further modified by cutting the rear off the turret to add a separate ammunition storage compartment with blow off panels. Also the engine is new and it has Kaktus-5 reactive armor tacked on plus composite side skirts. I think they may have reused a few bolts.

[Ritterin Sophia]

General Dynamics Land System offers an upgrade package for the M60 called the M60-2000 or 120S. It pretty much puts an Abrams A1/A2 turret, 120mm, and a new diesel engine and transmission in an M60.

[MKSheppard]

At what point does one start "looking into" a modernization for a tank too? What would qualify a tank for a modernization vs. just building a new damn tank?

The reason the T-55 has stuck around for so long is that it's a relatively simple design with a decently reliable mechanical drivetrain. The 100mm gun is still decent by modern standards. It won't score a long range kill on a modern 55+ metric ton MBT; but it can trash a whole bevvy of light vehicles. It also is of a caliber large enough for a decent HE/FRAG round, making it an excellent support vehicle.

If you take a T-55 and do the following:

• Mount an external laser rangefinder
• Replace the Commander/Gunner's optical sights with new passive infrared sights
• Install a ballistic computer that integrates with the old stabilizer or put in a new stabilizer -- and hook it up to your external laser rangefinder.

You now have a vehicle which can offer effective parity to 75% of the world's armored fighting vehicles, and offers significant overmatch versus 75% of the world's guerilla forces.

Here's a hint -- RPGs don't grow on trees -- it's very hard for any guerilla force to obtain anti-tank weapons unless they have significant external support or happen to raid someone's armories.

For that last 25% of threats; well that's what buying 50+ ton modern MBT is for.

But what makes these modernizations so attractive is that they're cheap. The Czechs will modernize your T-55 for $200,000 per tank, and their modernization covers pretty much all of what I listed above.

Since even the T-90 costs $3.5 million a tank; you can field 17 modernized T-55s for each shiny new T-90 you buy. These cheap tanks can then go into very high risk areas like COIN and be blown up with little financial loss.

Hilariously a lot of people seem to think the only thing you need for a tank to be the biggest and baddest is the biggest gun and thickest armour.

Actually, having a big gun and thick armor is required for MBTs. Otherwise, you die too easily, or can't kill the enemy.

Why do you think everyone is using guns equal to or heavier than 120mm almost exclusively for their MBTs now:

Leopard 2
Abrams
LeClerc
Arjun
K1A1
K2 Black Panther
T-64/72/90
ZTZ-99

And weights are in the 50 metric ton and above range? The Chinese ZTZ-99 has a weight of between 54-58 metric tonnes depending on the variant; the K2 weighs 55 tonnes, etc etc.

The only people who are outliers in this whole game are the Russians who keep flogging the T-64 design long past it's "Expire by date"; and try to make up the 46.5~ metric tonne weight by adding on ERA and active protection systems.

The gun for the T-90 is a very evolved version of the 125mm that armed the T-64; but it is increasingly falling behind because due to the basic design of the gun's autoloader mechanism, and the space within the T-64 turret; it is limited in the length of rounds it can load, even with split rounds (projectile + propellant). The Russians have spent a lot of R&D monies on complex sabot rounds that can have short penetrator rod lengths, but still have almost all the penetration of a long rod.

The Chinese for example long ago decided to grow their tanks to be heavier and to adopt their own 125mm gun which uses a autoloader design that pulls rounds from BEHIND the turret like like other Western tanks with autoloaders, rather than continue down the road of increasingly larger SCIENCE! expenditures to make a 35 pound bag hold 55 pounds.

Armour effectiveness has a lot more to do with variety of defensive systems than just some big slab of face hardened unobtainium.

No actually, you do need large slabs of unobtanium. The apogee of conventional armor in US tanks was on the M-60A3 Patton, which had turret armor with a LOS thickness of about 5.8-10 inches (depending on where you measured).

The first M1 Abrams had LOS thicknesses of 25.6" for the turret armor arrays; with later production models having longer turrets allowing 34.6" LOS Thicknesses.

This is because while advanced composite mixes using armor plate, ceramics, depleted uranum, etc are more mass efficient and easier to construct than the equivalent thickness of RHA armor; they are much less volumetrically efficient and harder to construct for complex curves.

[MKSheppard]

General Dynamics Land System offers an upgrade package for the M60 called the M60-2000 or 120S. It pretty much puts an Abrams A1/A2 turret, 120mm, and a new diesel engine and transmission in an M60.

At that level of cost, why not just buy the damn M1A2? If you're putting in the turret of the Abrams, that means you're spending a huge fraction of the cost there, due to the thermal sights.

[Sea Skimmer]

At that level of cost, why not just buy the damn M1A2? If you're putting in the turret of the Abrams, that means you're spending a huge fraction of the cost there, due to the thermal sights.

The gas turbine is extra expensive. The main reason why anyone is ever serious about turret replacement upgrades is you keep down the total weight of the vehicle while still ensuring you can mount a first rate weapon. The US won't export M1 tanks with depleted uranium armor, so export customers can't fully exploit the large inherent size of the M1 Abrams platform. I'd figure turret and engine replacement would be about 2/3rds the price of a new tank. Often tanks are upgraded in stages though; more pleasing to the budget.

[Pelranius]

The Chinese for example long ago decided to grow their tanks to be heavier and to adopt their own 125mm gun which uses a autoloader design that pulls rounds from BEHIND the turret like like other Western tanks with autoloaders, rather than continue down the road of increasingly larger SCIENCE! expenditures to make a 35 pound bag hold 55 pounds.

Some of the earlier ZTZ-99 versions (and most if not all of the ZTZ-96 variants) use the carousel loader type found in the T-72/90. The new, super duper 60+ ZTZ-99 with the new turret most likely uses the bustle autoloader (and maybe the variant that was driving around at the October 2010 parade).

[Marcus Aurelius]

But what makes these modernizations so attractive is that they're cheap. The Czechs will modernize your T-55 for $200,000 per tank, and their modernization covers pretty much all of what I listed above.

Since even the T-90 costs $3.5 million a tank; you can field 17 modernized T-55s for each shiny new T-90 you buy. These cheap tanks can then go into very high risk areas like COIN and be blown up with little financial loss.

Actually that's not cheap when you can buy a second hand T-72M1 with pocket money, which has a much better base armor, gun and mobility. In most cases it makes more sense to buy that and then have it modernized in a similar way; it's only marginally more expensive (if at all, in fact) and you end up with a more capable vehicle. If your needs increase later you can modernize the T-72 again with upgraded armor, thermal sights and the like. So in my opinion even "light" modernizations for a nearly 60 year old model make sense only if you are on a really tight budget and can't afford the fairly minimal cost of first upgrading your base vehicle to 1970s technology level.

About the T-72/T-90 type autoloader: the Russians have modified it so that it can now load much longer projectiles than the older models. The maximum length of the penetrator is of course still limited by the basic design, but much less so than it used to be, and making longer and thinner penetrators than it can now load is not easy in any case. The real problem with the carousel autoloader is that there is no way to make it as safe for the crew as turret bustle ammo storage (whether human loader or autoloader), if the armor is penetrated. The Russians have been trying to address that problem as well and it's somewhat safer now than it used to be in the baseline T-72, but there is no really good solution to that problem other than abandoning the carousel.

[Zaune]

On the subject of the T-55's main gun, instead of trying to cram a heavier weapon in there, why not take the opposite approach and fit something like a Bofors L70? It would free up space in the existing turret for modern fire-control equipment, and between modern APFSDS ammunition and a much-increased rate of fire I doubt there'd be a significant loss of lethality.

[CaptHawkeye]

An autocannon would rob the T-55 of any remaining chance is stands against modern MBTs and would leave it at a complete disadvantage against previous generation hardware. Autocannons are better suited for use on IFVs than tanks, even very old ones.

[MKSheppard]

The real problem with the carousel autoloader is that there is no way to make it as safe for the crew as turret bustle ammo storage (whether human loader or autoloader), if the armor is penetrated.

I was going to post something on this -- but saw that you got to it before me. Good man. That's a major reason why the Soviets used T-55 and T-62 for the Second Chechen war a lot -- because of their greater inherent safety if penetrated.

And good point on buying a surplus T-72 series and lightly modernizing it -- that would be a cheap solution for the "high end" of your military. M-60A3 is also an attractive option too.

[Marcus Aurelius]

On the subject of the T-55's main gun, instead of trying to cram a heavier weapon in there, why not take the opposite approach and fit something like a Bofors L70? It would free up space in the existing turret for modern fire-control equipment, and between modern APFSDS ammunition and a much-increased rate of fire I doubt there'd be a significant loss of lethality.

Increased rate of fire does not help that much if the ammunition does not penetrate... 40 mm autocannon would be definitely on the light side for a tank main gun, but a more reasonable alternative could be the Israeli 60 mm hypervelocity gun. It was specifically designed for modernizing light armored vehicles and it utilized a necked down cartridge of the OTO-Melara 76 mm naval gun, which gives the projectile a very high muzzle velocity. Still, with the latest APFSDS ammunition the 1940s vintage 100 mm gun is better and it can also fire a much more useful size HE shells.

The 60 mm HVM gun was actually used to modernize Chilean M24 Chaffee light tanks and in that context it made a lot of sense, because the original gun of the M24 was a medium velocity 76 mm weapon. The Russian are also offering a somewhat similar upgrade for the PT-76 called PT-76E, which replaces the original 76 mm gun with a 57 mm high velocity autocannon derived from the S-60 AA gun. The problem with that upgrade is that the Russians did not bother to design modern ammunition for the gun, so it's stuck with the 1950s vintage ammunition for the S-60. There is no sabot (APDSFS or APDS) ammunition for that gun, so the whole upgrade seems pretty pointless, but the Russians naval infantry apparently ordered some vehicles regardless, possibly because the modernization also includes a mobility and FCS upgrade. The new gun does have a significantly higher rate of fire than the original 76 mm gun, which can be useful for supporting infantry.

[Zaune]

I thought of the L70 because I've heard a claim that it's capable of penetrating the side or rear armour of an MBT when firing APDSFS rounds, and if Wikipedia's numbers are correct it has the same muzzle velocity as the T-55's current main gun, but fair enough. Still, an autocannon-equipped T-55 might have some potential as a slower but better-protected alternative to the Alvis Scimitar.

[Sea Skimmer]

The 40mm L70 sabot is rated to defeat over 100mm at 1km and 30 degrees, but this value should be treated with some quantification. The projectile is just 200 grams, vs. at least several kilograms for a tank caliber sabot projectile. While little projectiles can have very impressive penetration of a single solid steel armor plate, when you put them against a real life target in real life conditions it’s not going to work as well. Also at least in the CV90 turret the 40mm only has 24 rounds of ammo ready, which isn’t that awesome and indicates that the weapon is intended primarily for single aimed shots.

Smaller projectiles are simple more vulnerable to being damaged or otherwise performing erratically against armor features, like spaced armor, perforated armor, hard composites intended to shatter impacting projectiles and fragments and similar complex features. This is because of the simple reality that smaller projectile will have much more surface area relative to how much it masses and how much mechanical strength it has. So it takes more damage and sheds energy more quickly, while being easier to deflect and experiencing more disturbance in the air while flying to the target. It will also do less damage if it perforates the target; though that probably won’t matter if it hits fuel or ammo or several members of the tank crew.

Lots of stuff can defeat the side armor of old 40-50 ton MBTs, indeed on the and AMX-30 and Leopard 1 max armor thickness anywhere was only 70-80mm but I wouldn’t count on even 40mm defeating the flank armor on an 60-70 ton tank. Nor would I count on it to do a whole lot against an old tank given spaced armor even if this spaced armor is relatively simple material.

Also armor penetration trials assume a given slope of the armor plate, usually 30 degrees, but the target angle is zero degrees. As in the relatively target hull/turret at the time of impact vs. the axis the firing gun is laid on in ordered to hit a moving target. If both firing vehicles are moving then it gets even more complicated because the shell does in fact fly sideways through the air. So not often will you get that ideal zero degree impact reducing your penetration, to the point that at a significant target angle the projectile will just shatter or skip off.

The heavier range of vehicles can have very considerable flank armor in autocannon terms; the Tiger II had 80mm flank and rear armor, sloped no less, for example despite its relatively crude 1944 technology. The M1 is supposed to have more 100mm of base steel on the sides, plus composite armor and composite armor inside the side skirts. Your odds of defeating packages like this with even a heavy automatic cannon are bad unless you manage to pump in dozens of hits.

So an autocannon isn’t that viable of a dedicated anti tank weapon unless you have a very specific threat to deal against, certainly it doesn’t make a whole lot of sense as a replacement for a existing 100mm gun + ammo. At that point you now have a very excessively heavy vehicle for its armament, and that extra weight of vehicle still costs money in fuel and spare parts to operate. If you had no gun and no ammo, but a T-55 hull and turret then it might make sense.

The PT-76 upgrade makes sense because an automatic 57mm gun is actually bigger then a 76mm manual loader. The main reason for very heavy auto cannon is because now that people are building and planning IFVs that weigh over 40 tons you may simply need that firepower to take even the ‘lighter’ end of enemy vehicles.

If you want a minimal anti tank gun, I think it’s the 76mm on the South African Rooikat armored car. Reportedly, I have nothing to confirm this claim that was passed to me yet as of this moment, but it at least sounds right; the SADF 76mm gun was designed to defeat a T-62 tank from any possible impact angle at a range of 2,000 meters. It’s also confirmed that Rooikat was designed from the onset and prototyped with a 105mm gun, I has the pictures, but the 76mm was used because it was cheaper for production and could defeat any tank in southern Africa at the time. Specific threat at work. Mind you a 'normal' 76mm shell would weigh about 14lb while a 40mm shell is about 2lb. Sabot weights may not be in direct proportion to the HE shell weight, but its going to be roughly proportional.

[Sea Skimmer]

The new gun does have a significantly higher rate of fire than the original 76 mm gun, which can be useful for supporting infantry.

Yeah I think that's the idea. Use the 57mm to suppress bunkers, buildings and troops in the open as well as light-medium while you are making an amphibious landing. Tanks on the beach are priority targets for naval gunfire and attack helicopters. Once they have a beachhead they can bring ashore a lot of ATGMs and T-55s to cope with enemy armor. On land the 57mm should deal with Stryker class deathtraps efficiently even with its 1950s AP ammo. A lot of medium armor has serious protection against 30mm cannon fire these days but that's still nowhere near 57mm energy levels.

Found my copy of Rapid Fire BTW: the 60mm HVM defeats 120mm at 30 degrees and 1km range; not that awesome really. However that’s also operating with 1980s Israeli ammunition, an L70 with 2000s 40mm Swedish ammo is probably of significantly superior quality.

[Zaune]

Thanks for the insights, Sea Skimmer. This was my original source, by the way:

[Simon_Jester]

Armour effectiveness has a lot more to do with variety of defensive systems than just some big slab of face hardened unobtainium.

No actually, you do need large slabs of unobtanium. The apogee of conventional armor in US tanks was on the M-60A3 Patton, which had turret armor with a LOS thickness of about 5.8-10 inches (depending on where you measured).

The first M1 Abrams had LOS thicknesses of 25.6" for the turret armor arrays; with later production models having longer turrets allowing 34.6" LOS Thicknesses.

This is because while advanced composite mixes using armor plate, ceramics, depleted uranum, etc are more mass efficient and easier to construct than the equivalent thickness of RHA armor; they are much less volumetrically efficient and harder to construct for complex curves.

Excuse me Shep, could you unpack that a bit?

LOS thickness is... number of inches of armor that are encountered if you draw a line through the armor, yes? And when you talk about the "apogee," you mean the greatest thickness of steel plate, as opposed to the newer composite armors, yes?

On the subject of the T-55's main gun, instead of trying to cram a heavier weapon in there, why not take the opposite approach and fit something like a Bofors L70? It would free up space in the existing turret for modern fire-control equipment, and between modern APFSDS ammunition and a much-increased rate of fire I doubt there'd be a significant loss of lethality.

I'd think you run into another drawback by doing this, even if the autocannon has useful antitank capability.

Remember that the biggest reason to refit the tank in the first place, from what I'm hearing here, is to turn it into a "good enough" support vehicle that can back up the infantry while still being cheap and expendable. It's not meant to fight T-90s and M1s on equal terms, because it can't; it's meant to provide the bulk of the army with heavy AFV support.

In that role, it will see action blasting the enemy out of strongpoints and the like at least as often as it will be called on to kill enemy tanks, probably much more often. And autocannon aren't all that good for blasting the enemy out of places, compared to large-diameter shells from a heavier tank gun.

I seem to recall this being one of the reasons for the rapid escalation in gun caliber during WWII: it was discovered that it really makes a difference whether your tank can fire high explosive into enemy bunkers.

EDIT: Yes I know, antitank capability was a factor too, but very few tanks were designed purely to fight other tanks

[Sea Skimmer]

Excuse me Shep, could you unpack that a bit?

LOS thickness is... number of inches of armor that are encountered if you draw a line through the armor, yes? And when you talk about the "apogee," you mean the greatest thickness of steel plate, as opposed to the newer composite armors, yes?

LOS thickness is the thickness the shell would travel through if it hit horizontally, this takes into account the thickness advantage of sloped armor. So for a 30 degree sloped 100mm plate the LOS thickness is around 140mm for example. If armor is flat and vertical then true thickness and LOS thickness are the same. By apogee he does mean the best plain solid steel armor, though some of the 1945 US heavy tanks also had limited 10in thick armor.

I seem to recall this being one of the reasons for the rapid escalation in gun caliber during WWII: it was discovered that it really makes a difference whether your tank can fire high explosive into enemy bunkers.

You basically needed the ability to structurally demolish a bunker, though multiple rounds was acceptable for a tank, or else pierce the earthen berm in front of an anti tank gun and explode behind it to knock out the gun. A 75mm shell could do either job well; but anything smaller losses capability fast. 75mm is also big enough to ensure that you can accurately return fire at any possible range enemy anti tank guns will shot at you, 2,000 yards or more even in the days of WW2. Once more smaller stuff like 37mm simply went wild at that kind of distance. This is one of the reason for automatic cannon, one shell might be wild but two dozen will plaster the whole target area. The logic of the combined automatic and 100mm BMP-3 armament is pretty brilliant in the context of defensive suppression warfare I must say.. too bad its an utter death trap for the crew and squad.

[Norade]

I seem to recall this being one of the reasons for the rapid escalation in gun caliber during WWII: it was discovered that it really makes a difference whether your tank can fire high explosive into enemy bunkers.

You basically needed the ability to structurally demolish a bunker, though multiple rounds was acceptable for a tank, or else pierce the earthen berm in front of an anti tank gun and explode behind it to knock out the gun. A 75mm shell could do either job well; but anything smaller losses capability fast. 75mm is also big enough to ensure that you can accurately return fire at any possible range enemy anti tank guns will shot at you, 2,000 yards or more even in the days of WW2. Once more smaller stuff like 37mm simply went wild at that kind of distance. This is one of the reason for automatic cannon, one shell might be wild but two dozen will plaster the whole target area. The logic of the combined automatic and 100mm BMP-3 armament is pretty brilliant in the context of defensive suppression warfare I must say.. too bad its an utter death trap for the crew and squad.

Isn't the Bradley also pretty bad for crew survivability due to the high profile?