steel wool and foam to plug holes to prevent mice

I had a rat chew through the mortar inbetween the boulders that make up my fireplace chimney. We could hear him chewing inside from our bedroom 18 ft off the ground. I went up on a ladder and put the barrel of the 22 rifle in the hole with ratshot and pulled the trigger. Went down and got my welding gloves and reached in almost 16" and pulled his carcase out. They are tough critters.