Stop in for a cup of coffee

That's interesting. I just use what is in my hand or laying close
Carbine is a primary weapon.... pistol is secondary so if you're working with the carbine, you generally keep going unless it goes dry or there is a malfunction. If things are busy and there isn't time to resolve the malfunction, you transition to the sidearm.

If you're using Shotgun breaching, then you'd go carbine to Shotgun to conduct the breach, then back to carbine.

Fun stuff