Congrats on the G39! I run Gold Dot 200 gr. for carry, and practice with 185 and 200 gr. loads. I would also run 185 Gold Dot, as it performed well through mine, but it is rare to see that particular ammo around these parts for a decent price. I have enough 200 gr. to keep me in the game, so I just carry those in the gun and use G37 magazines for spares and also at the range.
Ammo by Dillon and Hornady