Rivet gun cuts in wrong spot?

I have a hand rivet gun but every time I use it (minus 1 time) I have to clip the stem off myself because the gun cuts it too far out (only cuts about 1/4"). Any ideas?

Specifications
Name: Hand Riveter Set
SKU: 38353
Brand: Pittsburgh (Harbor Freight, Might be the problem)
Grip: Material Vinyl

If you're using pop rivets, it sounds like you are using a rivet for thicker material than you are riveting. The rivet will snap at the weakest point which should be just behind the head.

If the rivet gun cuts the rivet pin, the jaws might be slipping on the pin so the jaws are not flush with the rivet when cutting. With some cheap rivet guns, you can get a better finish by pulling the rivet up to grip the material then releasing pressure on the grips allowing the jaws to reset and move further down the pin.