I had the very same problem with my Air Ranger, luckily it was within the warranty period but after three trips to the factory it still came back the same. They realigned the barrel and ended up replacing it but it was still rubbish so in the end I had it swapped from .20 to .177 by a great guy on here.
So he told me there is a very specific way and sequence to aligning the barrel on them and if not done correctly you will be shaving the pellets as they enter the breech.
For a change from left to right handed and the caliber swap plus service was less than £100 but that was last year. Very nice guy and excellent at his job.

HTH. Hal