For small arms and machine guns though — highlighting the differences between ball and hollow-point for pistols and SMG's, plus also SLAP for rifles and MG's, would certainly be relevant.
Hollowpoints: Only for civilians and war-criminals. Military small arms are supposed to be hardball fmj or equivalent. They're a war crime for the military to use, per the 1899 Hague Conventions. (While the US didn't sign, the US Military still follows them.)
I agree SLAP is VERY relevant. But also, it's only allowed in the anti-material role, shooting people is a war crime.
Hollow-points are indeed forbidden for military personnel to use, but not for civilians or law enforcement — and both can be found in the game among both PC's and NPC's, so I'd still deem it relevant to describe how their effect differs from ball in this setting.
Come to think of it, hollow-points would be relevant to describe also in rifle calibers, as pretty much all hunting weapons would be loaded with them. And you'd be certain to encounter those from time to time.
SLAP ... I am not aware that they're covered by the Hague Conventions. Are you quite certain?
The projectile from a SLAP is just a solid tungsten bullet. It travels at much higher velocity than normal bullets do, thus imparting a lot of kinetic energy, which makes it very efficient in penetrating armour, but in an unprotected target it just makes a clean hole; no tumbling, no fragmentation. It won't lose much energy passing through, hence it will also do a lot less
damage than a normal FMJ ball would.
This is pretty much the diametrical opposite to the effect described in the Hague Convention's "Declaration on the Use of Bullets Which Expand or Flatten Easily in the Human Body".
You don't want to use them against unprotected targets, that's correct — but not because they cause "unnecessary suffering" (which is what the conventions aim to prohibit), but simply because it's inefficient.
A lot more buck per bang, for a lot less effect.
they were banned, it would also mean that if you had SLAP loaded in a weapon, and were suddenly assaulted by unprotected targets, you'd have to change ammo before opening fire lest you were to become a war criminal. The risk would make it practically impossible for any force to field SLAP's — and we know they've been used in armed conflict since the 80's.