Yeah but with what you said earlier, tweak 7.62 ammos to make FN FALs better, that mean you should put 7.62 at same level or higher than .223 to be really usefull, and in this case you have big guns that will be impacted.
Not sure you'll have fun with all this, since M60 is actually weak, but if it become a second LSW, that won't do it, or there will be many raiders ingame

(or alts and this would be really poor :/)
So i wait to see the changes but here i don't think it will be easy, since balancing AR seems not that hard cause ammos have been balanced some time ago, for the others it will probably be a pain with lot of whining.