Sadr-Aldeen, an Iraqi Kurd, has seen business increase by 50 percent since last June, when ISIS militants took over Mosul, Iraq's second largest city, 82 kilometres west of Irbil.
The Kurdish fighting force known as the pershmerga has been at war against the ISIS militant group ever since.
Sadr-Aldeen says there is "no professional company" to fix all the weapons that "naturally break" during the fighting. "That is why I fix them. We cannot just throw them away, because we are in a war," he explained.
Aged 36, Sadr-Aldeen already has more than a quarter-century of experience, making him the peshmerga's top gunsmith in the region.
He says he now fixes eight to 10 weapons a day compared to a few during his pre-war business.
For three days, Sadr-Aldeen has been trying to polish the blood off an M16 rifle brought in by a pershmerga soldier last week. "It is an American made gun given to the Iraqi army in Mosul. Da'esh took it. It was in the hands of Da'esh (the ISIS group) and five days ago it fell in the hands of peshmerga," he explained.
Located in a cellar in Irbil's bazaar, Sadr-Aldeen's shop is a well-known spot for peshmerga soldiers.
Darawan Abu Bakr, a 28 year-old fighter, on leave from his post outside the city of Kirkuk, is a regular customer. Visiting the shop to have a weapon fixed, Abu Bakr said, "I have brought other weapons to Bakhtiyar (Sadr-Aldeen) as well and he repaired all of them. He is very good at his job.None of the guns he repaired have malfunctioned again. They all worked perfectly."
Now a father of five, Sadr-Aldeen has been working in the shop, which was started by his father, since he was a child. He took over the business when he was 11-years-old after his father was arrested by the forces of former Iraqi Dictator Saddam.
His father spent 10 years in prison and today is too old to work. Sadr-Aldeen also modifies weapons, taking special pride in his work fixing Kalashnikov rifles.
He showed off one weapon with a shortened barrel that makes it lighter and capable of firing more powerful bursts of ammunition. "I modified every single part of it.
The cover, the folding arm, the chamber, I made it fourteen years ago. It is all handmade," he said.
He also does not limit his work to his shop. Sometimes Sadr-Aldeen goes out to the front lines himself, mostly to repair heavy weapons that cannot be transported.
The peshmerga send a car and take him out to the front line to do his work. He said he does not charge for the battlefield repairs, saying that is his way of supporting the cause.