Sounds like fowling is definately a problem. Some powders are worse than others so you mught try different propelents to see which works best for your rifle. I do not see the need to remove the breach plug every five shots to clean the bore it may help to swab between shots from the muzzle end. This helps a lot when I shoot the old charcole burners that I shoot.
When hunting this should not be a problen since you have the rifle zeroed with a clean barrel and you will be hunting with a rifle loaded into a clean barrel.
Hope this helps.