I have a couple that need some barrel fouling to shoot their best. It could actually be the cleaning that sent it astray. I have one 30-06 in particular that took about 60 rounds without cleaning to get back where it was after I scrubbed the snot out of it with some " Remington 40X Bore Cleaner".
I wont do that again.
Now ill pull a bore snake through it once with a little Hoppes on the tail and push a lightly oiled mop through it after shooting and thats it.