Gary Strachen had gone into a rage with the victim following a row over £30.
The 46-year-old left the woman in tears when he stormed into a bedroom and brandished the firearm at her.
But, despite her obvious fear, she still managed to snap him clutching the gun on her mobile phone.
The photos helped him get caught for the crime and he was today jailed for more than five years at the High Court in Glasgow.
The woman was known to Strachen. He had been at her flat in the city’s Scotstoun on August 12, 2024.
The victim had called her mother asking for a loan of £30.
She agreed, but made an error in transferring the cash.
Prosecutor Kath Harper KC then explained: “This caused Strachen to become annoyed and an argument started.
“He screamed and shouted at her. This caused the woman to go into a bedroom.
“Strachen then burst in minutes later waving a sawn-off shotgun and pointed it at her.”
The court heard he went on to press the barrel of the weapon against the terrified woman’s cheek and then forehead.
The victim told Strachen she was going to call the police.
He replied: “Do it, go for it. Do it right in front of me.”
It was soon after the woman managed to capture Strachen brandishing the gun before he fled the flat with the weapon.
The woman dialled 999 then called her mum. She was described as “crying uncontrollably”.
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Strachen was not immediately traced, but the weapon was found wrapped in a towel at a unit he rented in Clydebank.
It was said to be “not a traditional shotgun”, but an old musket which firearms officers could not make safe.
It was in fair condition and was apparently in working order.
DNA linked Strachen to the gun. He was eventually arrested by police two weeks later, but made no comment initially about the incident at the flat.
Tony Graham KC, defending, today said it was accepted “such conduct cannot be tolerated”. He added “lifestyle choices” had led to Strachen getting in bother.
The court heard Strachen had 28 previous convictions for crimes including for violence, disorder and drugs, although had never been given a jail-term.
He was on bail for this latest crime.
Strachen admitted to charges of assault and possession of a firearm.
Lord Colbeck locked him up for five years and three months. The term was cut from six years and eight months due to the guilty pleas.
The judge: “You appear to diminish the effect of what you did by insisting the woman has forgiven you.
“It cannot be disputed that serious psychological harm was caused.
“However one looks at it, behaving as you did with a sawn-off shotgun reflects a high degree of culpability.”
After the hearing, prosecutors praised the bravery of the woman involved.
Moira Orr – who leads on major crime for the Crown Office and Procurator Fiscal Service (COPFS) – said: “Gary Strachen used a shotgun to abuse and terrify her.
“It is testimony to the courage of this woman that she managed to take photos of Strachen as he threatened and controlled her.
“Prosecutors were able to use these images to ensure that he faced the full consequences of his despicable actions.”
She urged anyone suffering or witnessing such offences to report the crimes and seek support, adding: “COPFS will use every means available to us to pursue justice.”