Air rifles on squirrels is a never ending battle. You kill 6 the first week and one a week for the rest of your life.
You need to close up the hole they are getting in through, and that is no small task.
FYI: squirrel hunting has a season and requires a small game hunting license, so if you are going to shoot them...KEEP YOUR MOUTH SHUT. Bragging about the 4 squirrels you just shot with out a license and out of season is a good way to get into big troubles.
I don't think you could get a critter out of a sticky pad trap with out A.) getting bit or B.) seriously injuring the animal. Sticky pads are designed to prevent the animal from getting unstuck and they do a good job of that.