Here's the things missing from the rules in that regard:
- Rules for falling velocity (penetration) over range
- Rules for composite armor
- Rules for reactive armor
Without those three things, you can't really
accurately represent modern vehicle combat.
The way I read this, it's only three things that would need to be addressed and given that T2K is mostly void of high-tech equipment, the latter two factors should come into play only sparsely. I'd still like to see rules for them, because that suits my approach on military wargaming and roleplaying. Also, at least canonically the odd T-80 or Leopard 2 will show up from time to time. One can of course discuss, if it's not more likely for characters to encounter T-34s or M-48s by the year 2000, but I'm all in for player empowerment and that means giving me (as a referee) choices, too.
APFSDS should definitely have more range, accuracy, and effectiveness against modern armor, many of which are all but impervious to HEAT (especially from the front). Most HEAT rounds simply cannot defeat any sort of modern composite armor or reactive armor. Is there still reactive armor around? I guess that one is up to you but it's probably 100% related to how much good ammo/ATGMs are still around!
As for cost/complexity... well, that depends. There's no moving parts really and no mechanic complexity, but there is a need for more sophisticated materials/metallurgy. You can maybe make an adequate HEAT round using more common knowledge and materials at hand than you could make a quality sabot round. (don't quote me on this, just how it seems to me)
SPOILER: Scroll down to the bottom of this text wall for my ideas.
Let me throw some rough ideas in. During the 1960s, tank designs were in an aporia. There seemed to be no armor protection good enough to guard against HEAT rounds, which could always improve penetration by enlarging the caliber, which added less weight to the tank than the additional armor that had to be added. Also, tactical nuclear weapons were doctrinal to the expected battlefields, nullifying any heavier armor than protection from medium caliber guns to the front and autocannons to the sides. Beyond that, speed seemed to be the better form protection over steel, since target acquisition was still relying on optical coincidence rangefinders and gun stabilizers were in their infancy. As such, first shot accuracy was abysmal, compared to the later Cold War and quantity of tanks seemed a solution over quality of accuracy. This aporia gave us the T-62 (I'm leaving out the T-55, because it's denomination as an MBT was retroactively introduced, the T-55 being the first true tank of that type it was developed as an improved T-54 medium tank), the Leopard 1 and even the M60 and Chieftain, which both tried increasing armor and not speed.
Composite armor becomes available after 1970. The first tanks equipped with these kinds of armors are the T-64 (all variants), T-72 (from model A onward, but leaving out the export version marked "M") in the USSR and in the West the M1, the Challenger 1 and the Leopard 2. By that time, the main types of ammunition to defeat armor were:
- APDS rounds, which superseded armour-piercing composite rigid (APCR) and armor-piercing, capped, ballistic capped (APCBC) ammunition, uniting all features positive about the two earlier types of ammunition: a hardened penetrator doubling penetration over wartime standards, high velocity, and low drag, allowing for velocity being kept at larger distances.
- HESH rounds, which are at thin metal rounds filled with delayed action fused plastic-explosive. The round squashes the explosive against the hull of the target creating heavy spalling within the inside of the tank, once the explosive goes off. Often, no penetration of the actual armor occurs, but the crew, equipment as well as the motive elements of the target are hit by extensive shrapnel, disabling the tank effectively.
- HEAT rounds, which produce a stream of hot gas that penetrates the armor, were the most effective during the 1960s, as the jet of hot gases formed the same independently from projectile velocity and as such targets could successfully engaged at all distances that allowed for the necessary accuracy. A technological downside of HEAT rounds was that the spin imposed upon the projectile by the rifling of contemporary guns inhibited proper forming of the jet. This problem had been largely countered by the Germans in World War Two by installing driving bands upon the casing of any HEAT round, absorbing the spin and thus not imposing it upon the projectile proper (to full effect). However, HEAT rounds did suffer somewhat from inaccuracy, when compare to APDS rounds.
Composite armor changed all that as it was supremely efficient against HEAT rounds by laminating steel to plastics, silicates and/or ceramics, which all had different hardness, thermal capabilities and durability, negating much of the jet stream formed by HEAT projectiles. At the same time, rifled guns were at the maximum of their velocity capabilities, since the rifling itself inhibited the acceleration of the projectile. The T-62 broke this dead-end by incorporating the first smooth-bore cannon and stabilizing armor-piercing rounds not by imposing spin, but by installing fins onto the projectiles. At the same time, HEAT rounds could be fired much more accurate from smooth-bore guns, if fins were added, too, also negating the need for driving bands. The T-62 did not feature composite armor, though, but the T-64 and T-72A did, at least to some degree.
Adding composite armor to existing designs was not possible at that time, but another form of protection allowed up-armoring against HEAT rounds. Explosive reactive armor was first used during the 1970s as well. The Soviets, again, were the first to field Kontakt-1 ERA around the end of the decade. First-generation ERA did not work against kinetic penetrators, such as AP(FS)DS, but provided high levels of protection against HEAT rounds, by damaging the jet and/or inhibiting its proper formation. ERA, due its natural explosive design (it's in the name!) posed a large threat to close by personnel or even soft-skinned vehicles.
Newly available APFSDS rounds matured during the late 1970s and became longer in shape during the 1980s. This allowed them to remain on a stable path longer, even while penetrating composite armor, diminishing its effects. This was necessary due to composite spaced armor becoming available, which deformed the kinetic penetrator by armored plates being set in vertical angles. HEAT rounds on the other hand, started countering ERA by employing a second, more powerful HEAT charge behind an initial, small charge, which set of ERA tiles before the main charge detonated. The effect of ERA was thus circumvented for the second charge.
A final generation of changes to the old race between firepower and armor came in the late 1980s and early 1990s with Kontakt-5 and similar second generation ERA, which now also worked against APFSDS long rod penetrators and applique composite armor becoming available, such as the German MEXAS. Also, composite spaced armor started employing spaced armor at varying oblique angles, negating to a large effect the advantages of early long-rod APFSDS rounds. In effect, next generation long-rods had to become even longer. This development, as well as the introduction of Tandem-HEAT rounds, also made ammunition noticeably larger than 30 years ago, diminishing the combat loads of tanks.
Now, how can this be implemented into the game?
First, I would argue that there needs to be some form of optional rules. Full implementation does not seem to benefit all groups in the same way, as details can quickly be overwhelming. Second, in my opinion, there should be attributes that can be easily applied to tanks and rounds to alter and denominate their game effects. These attributes would simply cancel each other out or modify the "Armor" modifier of cannon ammunition. Third, the armor values of vehicles should not be changed, but only altered by these new attributes. Also, smaller caliber cannons should have the same types of ammunition denominations as larger ones. There is no technical difference between a 20 mm armor-piercing round and a 125 mm round, both use discarding sabots and have used them for decades. Also, there are actually 40 mm HEAT rounds, like the M430A1 used by NATO grenade launchers. The armor penetration is actually not bad given the caliber, so why omit them?
What happened simultaneously to all these developments, was the introduction of laser-range finders as well as fully stabilized gun systems. At the end of the Cold War, first shot accuracy with APFSDS for western tanks (M1 or Leopard 2) was over 80 % at 3 km, while on the move. That would mean that rulewise such a shot should roll a pool of D12 + D12. This would include all modifiers, i. e. rangefinding, (digital) fire control system, stabilization, and ammunition.
Fire control systems and stabilization as well as rangefinders are encompassed in the Player's Manual p. 84-85, but should be somewhat expanded upon to accurately display the difference between an early model T-64 and a late model Abrams or Leopard 2. Likewise, the Player's Manual already differs between APDS and APDFS, giving the latter better armor penetration. This might be due to the caliber or combining both, though. Also, HEAT-MP ammunition, as used by western tanks (primarily with the 120 mm cannons), cannot be simulated here, since their properties would fall between HEAT and HE rounds and currently the stats leave no room for that. However, HESH rounds are introduced, as they have unique capabilities.
All in all, I think the following attributes should give more detail and make the different types of ammunition and armor more viable.
- Smoothbore [SMB], denominates a smoothbore cannon. This type of cannon always shoots fin-stabilized ammunition and thus infers a +1 Accuracy modifier when shooting. All other cannons are assumed to be rifled, as there are just these two types available.
- Composite Armor [CA], confers a +1 modifier to the Armor value of HEAT and APDS (but not APFSDS) projectiles. This is the original Chobham or Dolly Parson armor of the 1970s.
- Composite Spaced Armor [CSA], confers a +2 modifier to the Armor value of HEAT and APDS and a +1 to APFSDS projectiles. This resembles later protection system including non-explosive reactive armor or simple spacings.
- Explosive Reactive Armor [ERA], comes in two generations, ERA and ERA2. ERA confers a +1 modifier to the Armor value of HEAT projectiles, while ERA2 confers the same modifier to APDS and APFSDS projectiles as well. When a vehicle is hit the ERA tiles will explode, showering the hexes in the angle of attack with the equivalent of a 40 mm HE blast (cf. p. 113).
- Advanced Fire Control System [AdvFCS], received rules in the Player's Manual, but no tank is stated with one. At least the M1(A1) and the Leopard 2(A4) should have these.
- High Explosive Squash Head [HESH], these new type of rounds work are essentially high explosive rounds that inflict massive damage against a vehicles internals. HESH rounds have Armor values equal to HEAT rounds of the same caliber and crew of vehicles hit will suffer Explosive Hits one level worse than noted for HEAT rounds. However, HESH rounds cannot be fired from smoothbore cannons and are easily cancelled by all armor-related attributes: vehicles benefitting from CA, CSA and ERA will treat HESH rounds like HE rounds of one caliber size smaller.