Tuning Hatsan 135 .30cal velocity spread?

I have both, carnivore and 135. Now I haven’t run into that issue but I have heard about it from many other people. It could be something simple like bent skirts or something serious like a seal. They also have the ability to be pressured up if you have a Hatsan fill prob. Sounds more like it’s not sealing through the shot cycle down the barrel. Pellets or breech seal. I put silicone oil on my pellets. Try that first.