If you leave oil in your barrel, you will have a velocity loss of about 100 feet per second on your first shot. You can cure this by pushing 4 wet patches of Lighter fluid through your barrel, followed by a dry patch. Your cold bore shot now will be very, very close to a bore with 2 shots down the bore. Plenty good enough for coyotes for 300 yard shots.
1lessdog, at some point, you will need 600 or 800 grit silicone carbide paste from Brownell's
The very best abrasive compound for 'hard fitting' two pieces of steel. Stands up to continued fitting even on hardened and heat-treated steel. Silicon carbide grit combined with a thick, long lasting lubricant breaks down into smaller and smaller...
www.brownells.com
Or just take the gun to your gunsmith and he will put a new barrel on in it. 500 rounds of IMR 4064 in a Swift, you will not get the carbon out, and 50g of Retumbo with the 80g in a 22/6 Rem AI, in 600 rounds you will not have a barrel left.
We hunted in Mexico for predators from the late 70's to early 90's. Worst weekend was 13 and best was 56. A two week trip net was 226. We shot Remington 22/250's & 243's, custom 243's & 6mm Remingtons, and Ruger 220 Swifts. In between hunts, we went to the range and checked our zero, reloaded, chasing the lands from leade growth. Filthy barrels would go from shooting 1/2" groups at 200 yards to 3" groups at 200 yards. JB, Sweets 7.62, good bronze bristle brushes were our friend. Bores would be so filthy, we would just push 4 wet patches through the bore, then go straight to brushing with JB. 2" groups at 300 were acceptable, verified by shooting the 1 3/4" mini clay pigeons. Boys on our team took our equipment, trucks, and our calling sport serious as a heart attack. Our team had 3 trucks, a lathe, and we put 32,000 miles a year on our trucks calling predators.
When we got home from a hunt, rifles were put in a gun safe with one or more golden rods in the safe, cleaned as soon as possible from road dust that was horrible in the areas we hunted. Bores were cleaned, and we tried to get to the range to verify zero, if not, then the patches with lighter fluid/then dry patch had to suffice.