Does APFSDS shell size matter?

[InfiniteSpin]

Is lets say a 152mm apfsds shell more damaging than a 120mm one?

[highfivingbears]

I dont know about APFSDS in particular, but it stands to reason that the larger the caliber of the cannon, the larger the shell that it's able to fire. As such, it would make sense that a 152mm APFSDS would do more damage than a 120mm APFSDS.

[Rumpelcrutchskin]

Yes, from my experience the bigger APFSDS shell seems to do better post-pen damage.
The 120mm one feels pretty clearly better then 105mm one.

[OcGuy]

The bigger the shells, the more shatter (shrapnel) it produces in post-penetration condition thus resulting in more damage

[-NODER-_Novastorm_]

Apfsds most damage is delivered by muzzle velocity wich is n1 factor to increased damage, the more muzzle velocity the better another factor is the composition material they are made, this is why 120mm guns are the most popular guns used in mbts.
Look at Lclerc apfsds, that thing is awsome...

[MaDeuce]

E=mc^2

[HansGruber]

It's going to come down to velocity at impact, penetrator rod length, and material, more so than diameter.

Velocity can be added in a few different ways and yes bore diameter is one way. The 105mm Royal Ordnance L7 / M68 was, at a certain point, given a stronger breech design. Guns before that production change are prohibited from firing the M900 APFSDS which produces higher chamber pressure for more velocity. The M68A1 added a slightly longer barrel, again, for more velocity.

Increasing the maximum allowable chamber pressure, the bore diameter, and the barrel length (though this is not indefinite! Eventually more barrel length will REDUCE muzzle velocity!) will all give you greater velocity at the muzzle. You can do any one of those things, or any combination. Another option is to reduce projectile mass.

The rod itself is a much smaller diameter than the bore, and the trend has actually been to make rods longer and thinner. A thinner rod concentrates impact forces on a smaller area of the armor. A longer rod increases the maximum potential thickness of armor you can penetrate. When an APFSDS rod strikes armor, the rod and the armor essentially erode or vaporize each other, causing a tremendous amount of heat.

If the armor "wins", then either the rod will have been eroded to nothing, or have lost momentum and come to a stop inside a deep pit in the armor. If the rod "wins", then a white hot shotgun blast of armor and rod material come flying into the tank. If enough of the rod was still intact, you may also get long chunks of penetrator rod bouncing around in the tank, or if the armor was thin enough, you might even have the remainder of the rod exit the far side of the tank and do so with potentially enough energy to penetrate a second target.

The earliest rods were made from plain steel, followed by plain steel with various configurations of tungsten tips or inserts. The most lethal option are rods made from depleted uranium. DU seems to have a certain benefit that helps with armor penetration, but the biggest advantage it has is that it likes to burn when it gets hot. So if you tank is hit by a DU rod, you'll have that same white hot blast of rod material come flying in, but now it's on fire too.

[OcGuy]

Originally posted by Major Hans:

It's going to come down to velocity at impact, penetrator rod length, and material, more so than diameter.

Velocity can be added in a few different ways and yes bore diameter is one way. The 105mm Royal Ordnance L7 / M68 was, at a certain point, given a stronger breech design. Guns before that production change are prohibited from firing the M900 APFSDS which produces higher chamber pressure for more velocity. The M68A1 added a slightly longer barrel, again, for more velocity.

Increasing the maximum allowable chamber pressure, the bore diameter, and the barrel length (though this is not indefinite! Eventually more barrel length will REDUCE muzzle velocity!) will all give you greater velocity at the muzzle. You can do any one of those things, or any combination. Another option is to reduce projectile mass.

The rod itself is a much smaller diameter than the bore, and the trend has actually been to make rods longer and thinner. A thinner rod concentrates impact forces on a smaller area of the armor. A longer rod increases the maximum potential thickness of armor you can penetrate. When an APFSDS rod strikes armor, the rod and the armor essentially erode or vaporize each other, causing a tremendous amount of heat.

If the armor "wins", then either the rod will have been eroded to nothing, or have lost momentum and come to a stop inside a deep pit in the armor. If the rod "wins", then a white hot shotgun blast of armor and rod material come flying into the tank. If enough of the rod was still intact, you may also get long chunks of penetrator rod bouncing around in the tank, or if the armor was thin enough, you might even have the remainder of the rod exit the far side of the tank and do so with potentially enough energy to penetrate a second target.

The earliest rods were made from plain steel, followed by plain steel with various configurations of tungsten tips or inserts. The most lethal option are rods made from depleted uranium. DU seems to have a certain benefit that helps with armor penetration, but the biggest advantage it has is that it likes to burn when it gets hot. So if you tank is hit by a DU rod, you'll have that same white hot blast of rod material come flying in, but now it's on fire too.

Now this is a proper trivia regarding the said type of shell

[InfiniteSpin]

Originally posted by Major Hans:

It's going to come down to velocity at impact, penetrator rod length, and material, more so than diameter.

Velocity can be added in a few different ways and yes bore diameter is one way. The 105mm Royal Ordnance L7 / M68 was, at a certain point, given a stronger breech design. Guns before that production change are prohibited from firing the M900 APFSDS which produces higher chamber pressure for more velocity. The M68A1 added a slightly longer barrel, again, for more velocity.

Increasing the maximum allowable chamber pressure, the bore diameter, and the barrel length (though this is not indefinite! Eventually more barrel length will REDUCE muzzle velocity!) will all give you greater velocity at the muzzle. You can do any one of those things, or any combination. Another option is to reduce projectile mass.

The rod itself is a much smaller diameter than the bore, and the trend has actually been to make rods longer and thinner. A thinner rod concentrates impact forces on a smaller area of the armor. A longer rod increases the maximum potential thickness of armor you can penetrate. When an APFSDS rod strikes armor, the rod and the armor essentially erode or vaporize each other, causing a tremendous amount of heat.

If the armor "wins", then either the rod will have been eroded to nothing, or have lost momentum and come to a stop inside a deep pit in the armor. If the rod "wins", then a white hot shotgun blast of armor and rod material come flying into the tank. If enough of the rod was still intact, you may also get long chunks of penetrator rod bouncing around in the tank, or if the armor was thin enough, you might even have the remainder of the rod exit the far side of the tank and do so with potentially enough energy to penetrate a second target.

The earliest rods were made from plain steel, followed by plain steel with various configurations of tungsten tips or inserts. The most lethal option are rods made from depleted uranium. DU seems to have a certain benefit that helps with armor penetration, but the biggest advantage it has is that it likes to burn when it gets hot. So if you tank is hit by a DU rod, you'll have that same white hot blast of rod material come flying in, but now it's on fire too.

I like this, well thought out and answers many of the questions I have. Thank you

[HansGruber]

Glad you enjoyed it. I didn't throw this in earlier but here's an overview of how they evolved the rods themselves. Some of these, I think, are in game already, while most are not:

As I said, the earliest rods were made from plain steel, followed by plain steel with various configurations of tungsten tips or inserts. They were simpler and cheaper to build than the APDS of the era, which was essentially a miniature APCBC shell in a sabot. The APFSDS design also offered much higher velocity thus giving much better performance.

The Soviet 115mm 3BM-6 (Introduced with the T-62's revolutionary new smooth bore gun) and the 125mm 3BM-9 (115mm 3BM-6 scaled up for the new 125mm gun) were 100% steel rods. The 125mm 3BM-12 added the tungsten slug and the AP cap, while the 3BM-15 was merely a longer version of 3BM-12 using the same tungsten slug and AP cap. This additional length did add to penetration capability, however. The 3BM-22 was 3BM-15 with a much larger AP cap, again enhancing performance.

Take note that Soviet client states didn't always get the best technology available! Until the fall of the Soviet Union, the most advanced 125mm APFSDS exported was 3BM-15, completely ineffective against modern armor. In fact, the "export" version of that round, 3BM-17, had a more advanced AP cap but had no tungsten in it at all! 3BM-15 and 3BM-17 were both from around 1972, meaning that exported T-72 tanks were left using rounds that were nearly 20 years old by the end of the cold war!

Development of 100mm and 115mm APFSDS ammunition followed a similar path, however I'm not as familiar with it.

A curious oddity during this era was the 125mm 3BM-26 "Nadezhda" (1983). The design used a steel penetrator rod with an AP cap at the tip, but the tungsten carbide penetrator was kept near the rear end of the rod rather than the front, in an effort to improve effect against composite multilayer armor. Not sure exactly how this helped but it seems it did.

Eventually tungsten core sabot rounds would evolve to the point of having a nearly full length tungsten penetrator core, clad in a thin steel body to provide structural support. Examples of this include the US made 105mm M735 (1978), German 120mm DM13 (1979), British 120mm L23 (1985), etc. It appears that development in the west skipped completely past steel APFSDS, and straight to full length tungsten clad in thin steel bodies, although they would not have their APFSDS rounds in the field until some years after the first Soviet ones.

The relatively modern Russian/Soviet 125mm 3BM42 (1986, still in use, and apparently the most common round used recently in the fighting in Ukraine) is yet again a Russian oddity. It uses two different penetrating caps, two segments of tungsten penetrator filling nearly the full length of the rod, and they are held in place in the sheath with a low melting point alloy. Upon impact, the alloy melts, and the tungsten penetrators are free to slide out of the sheath and into the target, thus reducing energy lost when the steel sheath hits the target. The idea being that as the steel sheath is slowed down by the impact, the more effective tungsten penetrators won't suffer too much extra "drag" from it.

Obviously, at this point the sheath is wasted weight and space since it contributes little or nothing to penetration. Development was held up by trying to make one piece rods that were strong enough to do without the support sheath. Unless I'm mistaken, at some point tungsten rounds did eventually become 'monobloc' designs, though I can't say for sure when.


Depleted Uranium or DU penetrators didn't come around, as far as I know, until the 1980s. As I mentioned in the prior post, DU alloys have some properties that make them better at penetrating armor than tungsten alloys, and they also create more lethal post-penetration effects due to the pyrophoric nature of DU alloys. Again, the problem was one of materials, trying to get an alloy strong enough for the job.

I mentioned the 105mm M735 from 1978 as being a long tungsten rod clad in a steel jacket. The US was apparently working on M735A1, which would have been a variant replacing the tungsten with DU alloy. This appears to have been dropped completely, and development skipped to the world's first one-piece DU APFSDS round, the M774, in 1980. The design is a one-piece rod of DU alloy, with a ballistic cap, tailfins, and tracer attached.

The first US designed 120mm APFSDS to enter mass production, the M829 (1983) was of a similar design to the M774, using a one piece DU penetrator. The M829A1 (1988) was an elongated rod. Although much slower, the much longer rod gave the M829A1 incredible penetration, as displayed during the Gulf War.

The first US designed, although not produced, 120mm APFSDS was XM827 (1983). It was only accepted as an interim design until M829 development could be completed later that year. It was based on the German DM13, featuring a DU core instead of tungsten in a steel sheath.

Meanwhile, the Soviets developed DU rounds for their guns as well. The 125mm 3BM-29 (1982) was, much like the abandoned M735A1 and XM827, a DU penetrator in a steel sheath. In 1985, 3BM-32 came into service, featuring a one piece monobloc DU penetrator design.


I'm not sure about 100mm and 115mm designs, but all 125mm sabot designs the Soviets fielded during the cold war used "Ring Sabot" designs. The sabot is shaped like a disk or a ring, and the fins are full caliber to stabilize the round in the bore. This means a lighter projectile, and higher muzzle velocity, but also much more drag after the sabot separates.

All western designs used "Spool" type sabots, and most used sub-caliber fins to reduce drag after sabot separation.

Russian ammunition would switch to spool sabots starting in 1991 with the 3BM-46, being a one piece DU penetrator and also the longest round that could fit in traditional T-72 autoloaders. In the early 1990s, the 3BM-42M would enter service, being a much longer rod for more lethality (Comparable to the M829/M829A1 story) at the cost of only fitting into T-64/T-80 style, and more modern T-90 style autoloaders.

It appears that, with the introduction of 3BM-46/42M, the older rounds up to the 3BM-42 were cleared for export. No idea if the 46/42M or newer are exported.

There's been several new designs that I don't know anything about, 3BM-59/60/69/70, mostly for use in their various super-tank projects. Probably produced, but probably not in very large numbers.