HDB...

Take a small patch and coat it lightly with JB's Compund. Place the patch over a brush that is slightly smaller than your bore so the combination of the two fit nicely in the barrel( snug).
Run the rod up and down the barrel several times(10) and remove the patch. Is it dark and dirty? Good. Now repeat with new coated patch and do the whole process over again. Do three repititions of this and then clean the barrel with solvent to get the JB's out. Go shoot. Should be much better. If its better, but not up to your specs, try another bout of the JB method. If it still shoots poorly, you may have a bad barrel which happens from time to time with production run rifles. Check the forend pressure, bedding, crown and throat depth. Could be cut too deep.
Good luck.