I had trouble with mine at first. Tried all the adjustments listed by others, but decided to make mine not as pellet fussy. The barrel can be seperated from the breach block. It has 4 "claws" like a collet which allow the head of the pellet through but lightly grip the skirt.These claws can be adjusted and polished to accept a few different pellets of your choice that are of similar dimensions.Do not attempt this if you do not have good engineering skills, you can squash up the claws when re-assembling.
Baz