i had the same problem with a couple of my pistols, what happens is powder and lead deposits gets caught up in rough spots in the bore so even after you clean it those deposits work themselves out over those couple days of just setting, usually after shooting I'll clean the guns when i get home and then after 2 to 3 days I'll go back and run a couple patches through it again.

Something you can do to help smooth out the rough spots is get ya a jar of JB bore paste and next time you go shooting swab your barrel half a dozen times with the paste and then clean the gun up like you normally would after about every 50 shots do this till you have had 500 rounds through the gun. This is how I break in new pistols seems to do the trick nicely to smooth up the rough spots. just when doing this I would use jacketed ammo and save the lead cast stuff till after you finish this process. After you do that and if you still have the problem then maybe you might consider a new barrel just consider it though and try using the jb bore paste by swabbing the barrel first a half dozen time during your normal cleaning sessions after you are done shooting and if it doesnt work then you might want to seriously think about a new barrel because at that point your barrel would be about hopeless. in other words the jb bore paste should do the trick for ya. good luck