This will not be welcome news but I'll pass it along. Water dissolves carbon and Slick2000 carbon cleaner, among others is water bases. 409 Household cleaner is water based and takes out carbon. Lots of AR guys use such products on bolts, BCG. Now if you've a bolt action rifle, and the issue is getting all the water out of your barrel. Dry patches followed by Ballistol does the trick. I've use that on rifles firing black powder and corrosive ammo and I got British army funnel with chamber adaptor to pour boiling hot water down bore ...which dries instantly. Patch out the softened carbon .
All that is fact. Now...am I inclined to do this on a Accuracy International Rifle ? Different story isn't it...not some Enfield, Springfield or Mosin Nagant . At $900 per barrel from Europtics, my AI rifle isn't getting water in any form but I know water is the easiest remover of carbon. Could I pull the barrel off the rifle (my rifle is an AT so I could) and pour boiling water down bore and end the drama of carbon removal? Sure, its an option but then I got to re zero every 300 rd shot .
So ...putting the easy sure fire way off the table, I use Patch Out Liquid, I use it after I've cleaned bore with Hoppes and it will take out any carbon left in bore. This seems after 7 years to be a winner option.
Works for me but we all know bore cleaning is Voo Doo and all of you witch doctors are set in your ways.
On a parting note, today at range I heard:
"I put foam ear plug in muzzle, pour 50 50 solution ATF and Acetone down bore and let it stand 24 hours" Hmmmmmmmm last I looked foam ear plugs dissolve from Acetone so if this sage advice works, it puts 5050 ATF & Acetone all over your floor.
Being a smart ass ...I could not let this opportunity pass I asked if one could substitute Marvel Mystery Oil in place of ATF.....the soothsayer replied it might even work better than ATF. I am sure he'll try it.