The PAYDAY 3 CAR-4 unlocks at level 4 and appears as the M4A1 (CAR-4 Rifle) to other players.
The weapon shares stats with the CAR-4, excluding reload timers due to having ported PAYDAY 3 reload animations.
KNOWN ISSUES:
The mag is desynced during non-empty reloads. Will (probably) be fixed.
Q: How did you make the textures? Was it Substance Painter like RJC9000's PAYDAY 3 Lynx, or something else?
A: Short answer: It's a different way, and not Substance Painter. My way of making the textures for the weapon was to take the PAYDAY 3 normal maps, turn them greyscale, up the contrast and slightly decrease the brightness (via a Brightness/Contrast layer in Photoshop).