I like the spray in the barrel foaming bore cleaner
let it soak overnight and then using jags, keep running em until clean
then, a good thorugh working out with JB Bore paste
that stuff is awesome....
I had an old Sako 243 I bought used, did the usual quick cleaning, best groups were around an 1"
using the above method, shots were stacked at a 100 yards and sub 1/2" at two hundred