There's a simple modification you can make to a lot of Gamo triggers. I did it on a 440 Hunter DX (18 fpe springer) and a Gamo 640, as well as a Crosman Nitro Venom, and it transformed each rifle.
Make sure the rifle is unloaded and not cocked. Take the action out of the stock and see if there's a plastic roller behind the trigger that holds in place an L-shaped spring. If there is, you'll see that when you pull the trigger, this spring provides the 'first stage" (which isn't a true first stage).
The first part of the fix is to remove this spring. Drop the trigger from its housing by drifting out the pin at the front of the trigger housing. Drift out the pin that holds the L-shaped spring in place and remove the spring. Replace the pin and circlip.
The second fix reduces the pull weight of the trigger. To do this, put a washer over the rocker pin at the back of the trigger which engages the sear.
Refit, and you will have a trigger that breaks like glass, for next to nothing. The mod means that the trigger is engaged with the sear rather than the L-shaped spring, and the washer pre-tensions the sear to reduce the pull weight.
Watch Charlie DaTuna's trigger replacement video and you'll see which pins I mean. Also watch this irritating teenager's video and you'll see what I mean about the washer. http://www.youtube.c...h?v=5bBlS8adRTM Hope this helps.