There are several things to do that will help.
1) change to a different bullet will often times help.
2) try different seating depth's with bullet you are using.
3) try different bullet weight will also help.
I was loading for a guy for his 243, his 105 gr bullet starting shooting terrible, but after much testing with different bullets, what we found that really worked good was a 85 gr. bullet.
So his barrel was getting bad and it was time for a new one.