Assuming...
1. You have a good quality pistol in good repair.
2. You keep your finger outside of the trigger guard until you are ready to shoot (this means gun pointed at the target and sights roughly aligned before placing finger on trigger)
3. You use a holster.
4. You use the mechanical safety when provided.
...there is no problem whatsoever with carrying a round in the chamber. When you start violating these rules is when you will get a sudden loud noise when you really don't want one.
Note #4...some guns don't have them. If it is a good weapon in good repair, this is because it is not needed. Witness the DA revolver...no safety- no need for it. the DA trigger pull is stiff enough that it is not required. Witness the glock...a moderate pull, with associated other safety contrivances that make accidental firing impossible. However, with the latter don't violate Rule 3 of the Four Rules (or numbers 2 and 3 above)- that trigger is light enough that it can catch on something, or be tripped by someone playing around.
Mike