>>64466942
Nammo makes it easy by calling their 5.56 / 7.62x51 ammo by its weight in grams. M995 is AP3, 3.4-gram. AP4 is 4-gram and 62gr, core weight 38.6gr, AP45 is 4.5-gram (69gr).
RUAG's 5.56x45mm AP TC (Swiss P) is 62gr and therefore equivalent to AP4. AP45 claims better at-range performance. On an extreme end, Stiletto Systems has a 5.56 BS.45-5 with a 5-gram (78gr) projectile. Similar weight to Mk262.
https://www.stiletto.uk.com/home/portfolio/ammunition-technology/556x45/
7N39 is 61.7gr, so it's again directly analogous to AP4 / DM31. Since accurized steel core 5.45 is a thing (7N40) I could see them making a tungsten core version of that - similar to the relationship between steel core 7N45 and apparently a new tungsten AP .338 7N49. I imagine that's quite the performer.
>I mean, if the shield is on wheels, sure. Lightest armored vehicle.
Yeah, shields above M855A1 / 7N10M protection are almost always wheeled. Double limitation - backer technology isn't there yet and using B4C in a shield is cost-prohibitive.
>pic unrelated, new 3.5lb standalone M855A1 / M80 stopper called the LSAPI.
>pic unrelated, just AR500 armor being a dunce