
1. Make your model and so forth
2. When making your .weapon for your weapon go to zoom. For a simple, pistol, like scope do zoom level 1...2 to 2...for a sniper do levels 2..2 to 5 or whatever. You can make it zoom as many times (im guessing) and as far (still guessing)

3. open the weapon your got the gbx tag from and look for <name>.weapon_hud_interface.
4. save as <your weapon>.weapon_hud_interface
5. Scroll down untill you get to crosshairs...if you have a weapon that does zoom go to step 6. If not go to step 9
with:
6. look through the weapon_hud_crosshairs untill you get a zoom crosshair for mutliplayer.
7. Now in the bitmap you open and (if you want to change it) look at ui/hud/bitmaps/ and then sniper (pistol has none) and choose a sniper crosshair for zoomed.
8.(optional) If you have a custom one go to the folder you have it for and open it up.

without:
9. go to crosshairs and make a new weapon_hud_crosshairs. Make it a zoom for multiplayer.
10. For bitmaps look at steps 7+8
11. make a new crosshairs overlays.
12. change whatever you want. colors , anything
13. at the bottom of croshairs overlays is the flags. click only show when zoomed. and if you want different bitmaps for different zoomes make a new crosshair do zoom multiplayer. New bitmap. make a new overlay and click one zoom level.

this is also for making custom retulciles for weapons. Make a new aiming crosshair for mutliplayer...put in the bitmap and go ahead with the overlay. but you should click dont show when zoomed
hope this helps.