Is it normal for a FFL to ask for this

[2muchsoysauce4allthisrice]

This is the barrel in question, wonder if soaking it will mess with the gas block in some way? It’s my first time messing with Mcx style parts, even disassembly was completely different compared to regular ar

That’s quite a short boy. Not sure about the mcx. However, if it was just a regular direct impingement AR; I would be sure to hose everything down with CLP or oil everything after the water treatment. It’s the rust I would be worried about. You are going to shoot it anyways; so the excess CLP or oil should seep out once I shoot it. Don’t know if that helps.

If it were me, I would keep the water level low, so I don’t need to submerge the gas block. The water temperature should drop pretty quick with that little of water. You might have to go back and refill it. I would find a day where I have more time to go back and refill it with hot water again.

Even if the gas block is not submerged; clp or oil everything including inside of barrel after you are done with treatment.