Squirrel Proofing My Bird Feeder

[acruce]

I have a bird feeder that hangs hangs from a metal plant holder about 4 or 5 feet high.I also have a squirrel feeder in another part of the yard. Here lately the squirrels has figured out how to climb up the metal pole and get to the bird feeder. I was wondering if any of you had any idea's how to keep the squirrels out of the bird feeder. I am thinking of buy a big peace of PVC pipe to cover the the metal pole where the feeder hangs. I am hoping that will keep the squirrel from being able to climb up to the feeder. If that doesn't work I'm thinking of buy a pellet gun.