I am working on the lead in on the 9mm barrel

I am mounting on my 2240. I have been sanding the lead in to the pint were the pellet just fits. The O ring is pretty tight. I was curious so I tried to push the pellet into the rifling and it got stuck. I know that CO2 has about 900 psi ant PCP is even more. I just have no clue how tight it should be. Should I be able to push it through with out a hammer. (Did not use a hammer!)Running into enough issues as it is. Thanks