For some reason, I decided that maybe I should throw together a more "formal" vent hole cleaning kit. My two big guns have .200 vents... I believe that is a common diameter for 1/8 inch fuse or paper straw based "quills".
A .22 rod and brush is a little tight. I stumbled across something that I did not know existed. Apparently there are people shooting things that are .20-ish caliber. I dunno what, but there are apparently .20-ish caliber pistols as well.
Anyway, Dewey makes a 7 " long ".20 caliber" bore brush. The actual diameter measures about .158, so it should work fine on .186 diameter holes as well. The threads are 5x40 (I never heard of that untill last week either).
I also found a Dewey .20 caliber cleaning mop, a Tipton Bronze .20 caliber bore brush, and an "Iosso Eliminator" .20 caliber nylon brush.
I got them all from Midway.
They work a heck of a lot better than pipe cleaners and worn out .22 brushes. I especially like the mop for soaking the vent with water and Ballistol.