Cantom, a cheap and easy bore guide can be made from a piece of hollow plastic or a dowel, with a cartridge that has had the base drilled out large enough to allow your patch head and brush to pass through. The case butt needs to be glued or epoxied to the base of the tube.

Another more expensive method is to get a bolt, take out the fireing mechanism and remove the extractor head/bolt head and solder a drilled out cartridge to the base. To stop cleaners from draining back into the action/stock just slip a Buna N "O" ring over the case that will lightly seal the chamber.

I have a mixture of stuff that I make up for really difficult cleaning projects, It consists of 25% Cleens (automotive cylinder cleaner), 15% Kroil and 50% Brake Free.

Normally I use 50/50 Cleens/Kroil, but for really tough cases I use the above mixture. It really dissolves the carbon fouling that is between the layers of copper fouling and makes the whole process a lot easier.

I usually let the mixture soak for several hours before running a brush that is the next caliber smaller (7mm/.284) into the bore and pull/push back and forth several times at varying spots in the bore, a brass brush won't hurt anything. Then wipe it out a few times with a patch soaked with Motty's Bore Paste, a Parker Hale product, hard to find, JB bore paste will do the same job. Resoak the bore with the cleaner again and leave sit for seferal hours again. Clean out as before and Use Wipe Out or Sweets to finishthe copper and then swab the bore with alcohol to get rid of all the cleaning residue and oil the bore accordingly. You may have to repeat the above procedure mor aften, but it will do the job on anything I've ever come accross.