Yes they are adjustable, both 1st and 2nd stage and also trigger weight.
The trigger group is easily disassebled and honed with fine emery paper. You really dont need a mirror surface but the factory surface is very far from smooth. There are som sharp corners on the sear and the trigger lever, DO NOT ROUND THEM.
Pay close attention to the three small springs inside, if you get them mixed up the rifle will not lock.
This work will make all the difference in your rifle.
Just work slowly and with caution not to change the angles in the trigger geometry, all you want to do is polish the surface.
Tutorial can be found here
http://webpages.charter.net/guru1/documents/RSE%20Airguns%20-%20Beeman%20RS2%20trigger%20guide.pdf