Spring, Summer and Fall, I generally carry a SIG P365 with the 10 round Flush Mag in the gun. I carry two 12 round mags as back ups, so 10+1 + (2 x12) = 35 rounds. I'd love to buy a couple of the 15 round mags SIG now makes, but they are proud of those puppies.
In the winter or heavy coat weather, I carry either my Beretta M9 or Walther PPQ in .40 S&W. I keep the 15 round in the M9 and two 17 round mags, so that would be 15+1+ (2×17) = 50 rounds. The PPQ I keep with the 11 round in the gun and two 13 round mags so 11+1+(2×13)= 38 rounds.
In 9mm, I carry Hornady Critical Duty 135gr +Ps. In my .40 S&W, I use the Critical Duty 165gr + P. Both loads function well in their respective guns. In the P365, the Hornady holds a tighter group than SIG's Proprietary ammo for that gun.
Now, if I'm at home,.I'll throw on my carrier and grab my AR in .300 AAC. One 30 round in the gun, and six 30 round mags on my carrier. Two mags of 220 gr S&B Subsonic, the remaining five mags loaded with Hornady 125 gr HE'S.
To prevent confusion since I also own ARs in 5.56, I use P-Mags for 5.56, and HexMags for .300 AAC. This way I can feel the difference between the two magazines due to the pattern on the Hexmag. This way even in Low Light, I can feel the difference between the two types of magazines.