TLDR: Almost all of them are missing their best anti-armor rounds. Some that have all their best rounds shoot at the wrong velocity and thus have underperforming penetration. Some that have all their best rounds are still artificially neutered by either forced mixed belts or tiny 12-40 shot limits of their anti-armor rounds.
The only guns not from early WW2 which I cannot find any information on better rounds are the 20mm Oerlikons found on the Skink and the ZSU-37/2 Yenisei.
America:
Spoiler
- M19 & M42 Duster: The Bofors L/60 is Swedish in origin, and they developed APDS for basically every gun they made after WW2. This round is similar to the one seen on their reserve tanks, and would penetrate around 110mm. Also there’s nothing stopping usage of the 40mm APHE Sweden has either.
- Skink: I have no idea if the 20mm Oerlikons have any better AP rounds. My guess is its highly likely they had APCR at least.
- M163: known to be missing APDS rounds with up to 60-65mm penetration, comparable to the other 20mm autocannons that have such munitions.
- XM246: As discussed in the recent thread on it, there is nothing physically stopping this thing from loading NATO standard 35mm APDS.
- M247: No reason why the 40mm guns on this, derived from standard Bofors L/70 cannons, cannot fire their standard AP-T rounds (94mm pen) and APDS (125mm pen on L/70 Bofors, otherwise same shell as on L/60s)
- LAV-AD: It’s using the same HE rounds as Bradleys have at slightly lower velocity, which would imply that the same APDS and APFSDS used on Bradleys can also be fired by this.
- ADATS: also missing the same APFSDS the other Bradley derivatives get.
Germany:
Spoiler
- All APCR rounds currently ingame have below-historical levels of armor penetration, and overkill-neutered postpen damage.
- 20mm WW2 autocannons (Whirbelwind for example) still stuck with forced 50/50 APCR/HE belts years after that nerf ceased to have any relevance to game balance.
- 37mm Flak36/43/44: their APCR rounds are completely missing, a similar shell to but not the same as the one on the reserve tier 37mm gun for the Panzer III B/E.
- 30mm MK103: still suffering from an overkill 16-fold nerf to the APCR round’s postpen in addition to how globally bad APCR already is from all the way back in 2016. Also the use of the lowest possible estimation in its penetration at 77mm. Also the forced mixed belt of 2/3 HE and 1/3 HVAP. None of these nerfs are relevant anymore and all should be reverted.
- 20mm Rh202: Several platforms are lacking the APDS rounds for no justifiable reason anymore with the massive proliferation of light tanks. The Marder A1- and Leo2K are the examples in the German tree with this problem. Giving the Marder A1- a functioning gun would not necessitate it going up, since the 8.0 also has Thermals. The Wiesel, Luchs, and similarly light vehicles at the same or lower BRs get these rounds, so there’s no excuse here…
- 35mm Oerlikons: All are stuck with tiny 40mm emergency-use APDS belts, even though there’s really nothing stopping them from loading more.
- 57mm Begleitpanzer: Known to be missing APFSDS on its main gun for years despite 2S38 having comparable shell since its release.
- 30mm on the Turm 3: As this is arguably undertiered for what it can do, it should be given the Falcon’s APDS and punted to 9.0.
Russia:
Spoiler
- The 37mm on the ZiS-43 and ZUT-37 are missing the APCR belt seen on the ZSU-37. The ZiS-43 would not magically club with said shell as its still just a truck. The ZUT-37 is a known seal clubber, and giving it this shell would punt it up to where it belongs, alongside a global un-nerfing of APCR.
- 23mm AA guns on the BTR-ZD and Shilkas are missing APDS.
- ZSU-57/2 is missing its APCR rounds, which would pen the same as the round on the T-34/57 Mod’1943.
- ZSU-37/2: I have no idea honestly if APCR was developed for this gun, but as it was on its immediate predecessor the ZSU-37, it would seem likely.
- 30mm 2A38(M): Known to be missing APDS rounds on both platforms. The BMD series fires the same ammunition, so it likely would be the same performance as that gets.
Britain:
Spoiler
- All Bofors L/60s are missing APDS, already detailed above. Crusader AA Mk.1.
- Ystervark: Same gun specs as the Rh202, thus its highly likely this is missing the same APDS belt seen on other platforms with this gun.
- Crusader AA Mk.2 and Skink: Again, no idea if better rounds for killing tanks existed on 20mm Oerlikons.
- Bosvark: it’s using Russian 23mm guns, thus they’re missing the corresponding APDS rounds detailed above.
- Falcon: It’s got all its rounds, but is shooting at the wrong velocity - similar story to what was corrected with the Coelian this update. It does not have the same gun as the Fox, it has a longer barrel and should have higher MV and thus penetration, approximately 145mm on APDS. The APHE belt should also likely penetrate considerably more for the same reason.
- ZA-35: Also missing Oerlikon 35mm APDS like the XM246 for no justifiable reason.
- Chieftain Marksman: stuck with insulting 40-round limit on its APDS long after that nerf ceased to be relevant.
- Stormer AD: Another 25mm Bushmaster missing APDS and possibly APFSDS seen on other platforms with the same gun, for no reason other than “its an SPAA.”
Japan:
Spoiler
- 20mm Type 98: No idea if better rounds existed for this gun.
- M19, M42, M163: same issue as American copies regarding missing rounds.
- Type 87 SPAAG: same 40-round artificial limit for APDS as on many other 35mm Oerlikons. Especially egregious considering the Type 89 IFV has the same round on the same gun in limitless quantities.
China:
Spoiler
- M42 Duster has the same issues as the US copy.
- 25mm PG87: Missing APDS on its main guns, affecting the ZSD-63 SPAAG, the ZSL-92 light tank/SPAAG hybrid, and the PGZ04A high BR SPAAG.
- WZ305: missing same APCR the ZSU-57/2 lacks.
- PGZ09: same 40-round limit on APDS seen for most 35mm Oerlikons
Italy:
Spoiler
- M42 Contraereo, L6/40 & copy, AB41, AS42: suffering from the same APCR nerf globally as well as forced mixed belts like the Whirbelwind, despite never being a “problem” once in its ingame existence.
- Leopard 40/70: All Bofors L/70 guns are missing APDS with 125mm pen, and there’s technically no reason they lack the same APHE the Swedes get either.
- R3 T20 FA-HS: Same gun dimensions and specs as the Rh202, therefore there is more than a good case to give it the same APDS rounds most other platforms with it get, and un-nerf its stabilizer. Then punt it the hell out of WW2 BRs like was done with the twin 106mm version.
- Italian ZSU-57/2, ZSU-23-4V: same story as Russian originals.
- SIDAM 25 & Mistral: stuck with the same 40-round limit on APDS as the much-deadlier 35mm Oerlikons get for no good reason. M113 chassis is a box with limited mobility and no armor to speak of, a far cry from the Gepard (Leo 1 chassis), ItsPv (Leo 2 chassis), or even Marksman (Chieftain chassis). Several IFVs get the same ammo in as much as they want in the same tree.
- Otomatic: still stuck with 12-shot limit on its darts, in addition to global postpen neutering of all smaller-caliber darts. Totally forgot this one.
France:
Spoiler
- AMX-13 DCA40: Same story as other L/70 Bofors regarding APDS and APHE.
- AMX-30 DCA: Same story as Falcon, as its using the same gun.
- Many high BR tanks use 20mm autocannons derived from the Rh202, fire the same ammo, but lack APDS much as the Leo 2K does. No justifiable reason here.
Sweden:
Spoiler
- Lvkv 42 and VEAK 40: both missing APDS developed for and used by both guns. It is also questionable that the AP and HE rounds see a noticeable velocity and pen increase but the SAPHEI does not - likely this is not correct if I had to guess.
- USH 204 GK: same story as other Rh202 derivatives in lack of APDS for no justifiable reason.
- ZSU-57/2: nothing new here, same as other copies.
- ItPsV Leopard: Stuck with same 40-round limit on APDS as other 35mm Oerlikons long after that old nerf ceased to be relevant.
- Pbv 302 BILL: I pity whoever can attempt to play anything with 48mm pen APCR at 8.7…
Israel: nothing unique here, nothing to mention not already covered elsewhere.
Note: I may have missed something, please correct me if I did and I’ll add it to the list.