As the other man retreated he was struck in the chest with the gun. The injured man and his passenger wrestled Marsters back against his car bonnet but he managed to free his hand and fire two shots which struck the victim in the face and in the bicep.
Staggering to the ground, the victim was then hit several times about the head with the pistol.
The Court of Appeal judges noted Marsters' 30-year history of violence and drug offending and his lack of remorse. He had been a serial offender all his adult life and had been imprisoned on numerous occasions.
They said they found submissions on the length of the current sentence "unpersuasive."
"This was without question a case of very serious violence," the judgement reads.
They accepted the sentencing judge's assessment of the totality issue "in all the circumstances" and dismissed the appeal.