You can buy Simply pellets from Pyramid Air. Unfortunately I think they only make them in 177. They have screwed on lids and at 10 meters from a rest with my FWB 300 s I put five shots in the 10 ring, three through the same hole.
I would add besides lubing the o rings use caution when pushing them past the openings in your tube as the sharp edges can cut the o ring. I push them down with my finger as they enter these areas