RE: Range work ??
Start by speaking English. A 9 twist will stabilize a 150 grain 30 cal. bullet with absolutly no problems. You can't have a lead build up with a jacketed bullet. If your happy with a 3" group at a 100yards you need to spend some serious time at the range. At a 100 yards and a factory gun your wasting your time sorting anything, Spend a little time with load development. Buy the Sierra manual and go with the accuracy load. If that doesn't put you into the 1.5" to 2" range throw the gun in the dumpster and buy something new. I have plenty of factory guns that stay in the 1" to 1.5" range. a couple that will shoot consitantly under an inch.
You may have really bad Copper fouling and the only way to get it out is with some serious cleaning. I like Sweets for Copper. There are plenty of good copper cleaners out there. Anything with amonia will clean it out. Run a patch of Sweets through the barrel and wait 10 minutes or so then run another through. That patch will be the prettiest color blue you ever saw. The bad thing is Blue is the reaction copper has with amonia. run 'em through untill you see no blue. Don't use a bronse brush because it to will come out blue too becuase it will also react with amoniaJust a cotton patch will be the best bet. Make sure you have the carbon out as well. You could have a layer of copper then carbon. Sweets will not attack the carbon.