Double Rifle

Hi. I am wondering if any forum members would know how, or if, the temperature in spray booth will affect the regulation of a double?
I am getting the breaches of my double Cerakoated, as bluing does not give a satisfactory result for the 4 inches or so of the breach. The breaches are made out of different steel to the barrels apparently, but to rectify the problem once the coating is applied it goes into a room that reaches either 150 Celsius for an hour or 120 Celsius for two hours.
Do...

Double Rifle