Those are the weapon tiers:
CV = Conventional, MG = Mag and BM = Beam tier

Originally posted by Musashi:

Those are the weapon tiers:
CV = Conventional, MG = Mag and BM = Beam tier

Thanks for the swift answer! But are they all like that? I'm currently not at my home PC, so I can't check, but I believe there is also a perk that gave a -/-/- bonus to certain types of weapon? (I believe more "normal/non-alien" weapons)

EDIT: Where can I see which weapons are ballistic/non-ballistic?

Tier 1 starting weapons are referred to as either conventional or ballistic by many sources (perks, mod descs, etc). Magnetic (also covers gauss weapons) for tier 2, and beam (or plasma) for tier 3. Just how many people use TLE and TLP interchangeably to refer to The Legacy Pack, (I'm a TLP person, myself) you'll find a lot of alternate terminology for things with XCOM 2. Not ideal, but it's something you get used to, and it makes sense in most cases.

The other RPGO damage perk you may be thinking of is Old Guard which adds +1 to a soldier's damage when using conventional/ballistic/tier 1 weapons. If you're playing with options to choose your perks, I wouldn't recommend Old Guard (even if it could be considered thematic) unless you plan to delay mag weapon research for a significant amount of time. It's one of the perks I remove from the game, simply because I prefer game mechanics that apply over the full course of a campaign, not just the first two months where those extra damage points won't do anything except overkill basic troopers.

Thanks!

Its starting to become clearer to me.
Yeah, I'm choosing the squaddie perks myself, might switch that to randomized, both for the sake of simplicity, as well as for the sake of stopping myself from picking the same few, very useful perks for all my soldiers... :)