Gonna talk about the HAK first since the PP-19 part might be a long post. Please make it so Support can self-supply with the Heavy Ammo Kit. Oh that is too OP you say? Then why do medics get to self heal with their medic kits? If having (quasi) infinite lives isn't too OP then neither is having infinite ammo.
~~24-round mags for the Glock 18 maybe? I know it can be quite strong in CQB but 19 rounds for a gun like that is just… cmon. Plus 5 more rounds a mag simply can't all of a sudden make it everyone's go-to sidearm, I still get smoked by the MP443 and Unica daily
~~ Never mind I just need to unlock the extended mag, who needs sleep or a life anyway 
The PP-19 we have in the game right now is actually the PP-19-01 "Vityaz" SMG, which is different from the PP-19 "Bizon" (notice how it's actually designated the PP-19?) that uses a 64-round cylindrical magazine.
I recommend renaming the PP-19 in game to PP-19-01 to avoid any confusion or just remodel it to be the Bizon, like I suggested with the M9 and BHP not long ago.