I watched a couple of videos that cautioned about being careful with even the 10mm screw. They said it could make the gun unsafe by going off with a slight bump. I used the 8 in mine. Yes the trigger still not worthy, just a little less now. But now I have two HW guns so my Gamo never gets used.
I don't remember or know what trigger I have in mine. It is a Swarm Fusion gen II. Honestly though, having tasted the triggers in a Wierauch, I wouldn't throw any more money at the Gamo. Put it toward an HW 50.
Disclaimer: I don't have a CAT triggered Gamo but I am familiar with them. I do have the older metal bladed Theoben based Gamo triggers and the later Gamo SAT trigger. The CAT is Gamo's newer design.The CAT trigger is the same as the SAT trigger with one exception. The SAT only has one adjustment screw whereas the CAT has two adjustable screws. The additional adjustment screw in the CAT is installed in the actual trigger blade and makes for a much improved trigger over the SAT and earlier Gamo triggers. I subsequently modified all my SAT triggers by adding the additional adjustment screw the CAT provides.The CAT forward screw is threaded into the actual trigger blade and the rearward screw is threaded into the aluminum housing. The attached illustration diagram refers to the trigger blade screw as the "regulation first time screw" and refers to the second adjustment as the "regulation sceond time screw". The second screw is the one requiring the most scrutiny.The second screw (oem) cranked fully clockwise until it stops is normally safe. Using a longer second screw is where folks often get into trouble. A longer screw used here is alot like a pet rattlesnake. Fine today, who knows tomorrow? The trigger blade screw otoh can be cranked clockwise quite a bit without problems and that's what I do. The CAT trigger is not a true two stage trigger but with some tweaking it can be a pleasant experience. Adjusted correctly the trigger is pleasant, predictable, and fairly light. Crank down the forward screw in the trigger blade clockwise a lot and crank clockwise the rearward oem screw till it stops. Makes a long 1st stage, hit the wall, next light squeeze and the sear releases. Very similar to how I have my Diana T06, HW Rekord, and TX200 setup but with a longer pull distance.The 12mm screw mod mentioned by others: Before adding the second screw to my SAT Gamos I had a Gamo (SAT) underlever set up with the longer 12mm replacement screw for years. Shot it without problems until one day... Cooked it and BAM! Unintenional discharge that bent the cocking lever and did my fingertips no favor. I removed that screw, reinstalled the oem screw, straightened the lever, sucked on my fingertips over a couple bottles of beer and decided to solve the problem by modifying the triggers like I described above. FYI I prefer the modified SAT or CAT over the CDT/GRT triggers (I have guns with those too).
Pointing the tip and polishing the tip the 8mm screw will make a big difference. As far as fun I have two QB78s have had them for about six years great guns, accurate very mod friendly but they doin,t come close to the Swarm Mag Gen 2. I have had my gun for just a short time has taken a truck load of critters let alone it's paper punching accuracy with the evil, cheap CPHPs. The more you shoot it the better it gets, let alone the gen 2 inertia mag. I forgot to say I also have a HW95 in.177. What can you say bad about the 95 nothing but it does not have the Mag. and in the heat of a starlling war or a dog food can shoot off off handed at 5 to 75 yards I will take the Gamo every time. Way better than fishing. Forgot to mention that I have 3 tins thru my Mag Gen 2 and no problems. It get some pretty rough use and keeps on producing. Mike
I had the same problems with my loader. I got so fed up I just took it off and used the gun like any other break barrel.