They are not any stronger than other infantry weapons, I do not see why. M1919 is getting nerfed in terms of not being able to grab two on a single squad, I think that's plenty enough.
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I do not consider BARs as overperforming...
I defintely consider US lmg upgrades superior to "other infantry weapons", for example I would pick BARs or M1919s over PPSHs every single time if I had the option (all costs included). The ost lmg upgrade on grens is imo comparable but at least there is only 1 lmg on a 4 man squad. However I would welcome all lmg upgrades (BARs, M1919s, LMG42s) on basic (BASIC! i.e. not elite) infantry toned down, as it makes the basic infantry too good imo.
We`ll just have to disagree on this one, which is fine of course.
BTW: I have to say Milka raised some very valid points/concerns, interesting...