Thanks Malgus. I prefer a mapp gas torch. Sometimes I use it with wd40. There are bolts so badly rusted they never come off. The point of wd40 is not to break them off in the hole and give yourself an even bigger problem. You have to have the touch and feel if they’re going sheer off or just come out really squeaky hard. I always prefer grade 8 bolts. Of course there are some things it’s easier to cut off with an air grinder. No point in trying to save them. Hard to tell with guns but I’ve seen some heavily rusted barrels that were firing corrosive ammo. Maybe the MP would clean them out. I’m not up to carrying out that experiment though. Rennovating really old guns would be cool. Or dangerous as the case may be.