The officer inadvertently discharged the weapon in a designated firearms room at Ayr Police Office on March 23 this year.
The bullet hit a brick wall and no-one was injured.
An investigation by the Police Investigations & Review Commissioner (PIRC) found the discharge of the firearm was negligent and preventable.
Investigators found Police Scotland practice and procedures in respect of firearms safety are "stringent" and that if standard practice and procedures had been "rigorously adhered to", the incident would not have happened.
Police Scotland has taken action to re-emphasise the importance of adherence to firearms safety procedures to all its firearms officers following the incident, PIRC said.
The commissioner, Professor John McNeill, said: "It is clear that Police Scotland's practice and procedures in respect of firearms safety are stringent and had they been rigorously adhered to, then this incident would not have occurred.
"I am pleased that Police Scotland has taken action to re-emphasise to all its firearms officers the importance of adherence to firearms safety procedures following this incident."
Whenever a Police Scotland officer uses a firearm the chief constable must refer the matter to the PIRC for independent investigation.
As part of the investigation, PIRC investigators interviewed the police officer who fired the weapon.
They also reviewed witness statements, examined documentation, productions and command and control records.
A Police Scotland spokesman said: "Strict processes and procedures are in place which should be followed when weapons are being handled.
"Unfortunately, during the course of cleaning a weapon those processes were not adhered to.
"Following the PIRC investigation there is no requirement for Police Scotland to amend the processes referred to."