Well let me throw my 2 cents in here. I disassemble the rifle, take the nipple off of the barrel (throw that thing in a small dish with HOT water, I do that now because I dropped one down the sink in the past, some of you may recall that post
) Then I fill a small wash tub half way with HOT water and DAWN straight out of the water heater. Then with the nipple end of the barrel in the tub I take the cleaning rod with patch and run up and down the barrel. It sucks water in through the nipple. then hook the garden hose to the water heater and spray it down with hot water. Then its off to the oven at 200 degrees till dry. Then its WD40 time. Then after that evaporates if I'm not going to use them I coat the bore with bore buttah.
The GPR barrel will not fit in the oven so she gets dried with an old hair dryer that SWMBO gave me.
Oh if your water heater is inside your house you may have a hard time doing it this way