Gamo Hornet schematic

Ok, set your air rifle in a Vise.
Take a target, look down the barrel of the air rifle and move the target until it is centered on the hole in the barrel.
Adjust the sight until it is centered on the target.
After that the only thing that you need to do is adjust for the range (distance/elevation/vertical setting) of the target.

Regards
Geoff

Bone Collector .177 and .22 cal special edition air rifles ...

www.gamousa.com > Air Rifle
The "BONE COLLECTOR" .177 and .22 caliber air rifles. ... blast reducer integrated into a bull barrel, and utilize the advanced IGT (Inert Gas Technology).
images for Bone Collector .177 Caliber barrel

http://www.airrifleshop.co.uk/Airgun%20manuals.htm
Has some gamo manuals not the specific one you want but has all the important info for safety and operation plus zeroing if its a parts diagram you want look at the following link
http://www.aceros-de-hispania.com/MANUALES-DESPIECES/DESPIECES-CARABINAS-GAMO/despiece-silent-stalker.jpg

http://www.brownells.com/rifle-parts/sights/front-sights/index.htm

Does this video help...

https://www.youtube.com/watch?v=nmi6I2mceQs&index=2&list=PL134D25F90CAA8A8D

I have a similar Gamo air gun and the serial number is on the barrel on a flat spot on the side near the hinge.

I'm not familiar with the scope, is it an air rifle scope? One stroke type? If not, the backwards recoil of the air rifle is tough on a normal scope, they aren't made for that type of abuse. They work fine with a normal recoil. That is why they started making air rifle scopes. I'm sure that the internals of your scope are damaged somewhat, you can take off the eyepiece no problem, you might find something in there, loose screw, missing screw, you never know, don't get too carried away with the dis-assembly, you'll never get it back together. It sounds like the magnification ring is messing with the focus of the eyepiece. Might just need some oil. Hope this helps.

got the owners manual off the internet and reassembled it. works good!