Breechplug
Boiling Water is Bad, like Semisane said it causes Flash Rust
Your kidding me that is one of the best ways to truly flush the bore of the barrel. It opens pores releases all the oil contaiminates and dislodges plastic fouling. I have been using that method for years and will continue to do so. Flash rust on a blued barrel is minimal and no worse that the rust that occurs when blueing metal.
All of my ML's get that treatment at least once a year... If I were shooting BH the need might not be as great but for getting contaminates out of the bore it is great. The boling wateralso helps dry a bore much quicker than using hot water.
Another advantage it is so easy to treat and get a lasting treatment of a bore when it is hot... the pores are open and treatment can leach out the old fouling. Maybe that is one of the reasons that I do not get the 'crud ring' when shooting T7.
I know there are a lot of people that think you can not condition a bore - but metal is metal and metal has pores and hot metal makes the pores expand and easy to clean...
Just my two cents...