Ok... so an update on my situation. I went to the range yesterday and it's still happening. I tryed all different kinds of ammo from birdshot to 00. I pumped the action aggressively... and I still seem to have the same problem. I'm going to have to take it down to my gunsmith to have it checked out and fixed. Thanks to everyone for your help and input.
Sorry you are having problems with your 870. Hope you get the gun running good. A good running 870 is a joy!