Why don't machine guns have scopes? - Optics

Oversize rethread the mounting point if possible and use a larger screw

http://i3.squidoocdn.com/resize/squidoo_images/250/draft_lens17662396module148380681photo_1298220589crosman-classic-2100-2104
Hope it helps.

It is most likely the mounts not the scope. I would just install it on the new gun and check it there. Most times a scope that wanders is the mounts. One thing with big scope is they need to be tight or the recoil will move it in the mounts. Next due to being tight when the gun heats up it can and will tweak the scope in the mounts enough to move your center. Try it in your other gun, try 3 shot groups and let the gun cool. Recheck your center. If it is good with a cold gun all is well. If it moves from one day to the next it is the mounts. If you count the clicks to recenter, come back the next day and move it the same clicks, it is the mounts. If it is all over the place, day after day it is the scope.

Most of the time a scope that creeps off its zero, has a loose mount screw and or loose mounting ring. Check the mounts all screws. Some times the opposite is true. The mounts are to tight and in a bind. Then during firing the receiver heats up an tweaks the scope enough to cause creep. If the scope is always on zero when cold and creeps off after a few shots, she is in a bind. Make all adjustments to the scope base and rings with a cold gun. Loosen the front ring screws first then re-tighten then loosen the rear doing the same. Then try and re-zero the gun. If the gun never comes back to zero, you end one day shooting hi to the right and try again the next day shooting in the same spot try to re-tighten all screws. Screws from mount to gun then scope rings to scope body.

the only way to find cheap caps it try a fuw gun shops to see it they have any old scope that dont work and buy the caps that will fit your scope most gun shops keep old broken scopes just for that?

should be the same as any other rifle scope. Go here for excellent instructions:

http://www.outdoorpros.com/How-To-Guides/How-To-Zero-A-Rifle-Scope/5

You probably have rings designed for a standard Weaver style scope base.... you need "3/8" groove .22 style" rings... available from your local gun shop.
Hope this helps, Mark the Gunsmith

Please give feedback!

First is to try for a group, do not adjust the scope in any way. Shoot 4 rounds with out adjusting the scope. The gun should settle down and start to group. If you can not get a group in 6 rounds go clean that gun & check your ammo. Start over. If she does not group, its the gun not the scope. Once it starts to group move the cross hairs in the opp direction small clicks and "TAP' the scope after each adjustment. Shoot for a group each time 2 rounds should group. Get a target that has a grid to help get on faster. 

Probably the rings on the scope have loosened and the body of the scope has pivoted to the left. To correct it, you need to put the gun in a gun vise or in a cleaning stand to hold the gun straight. Then you would need to confirm that the scope has tilted to the left. You will have to loosen up the rings and turn the scope so that it is upright. The best way to make sure is to use a scope level. Lay the scope level on top of the scope turrent to confirm that the top of the scope is level. Sighting thru the scope you should be able to confirm that the cross hairs of the scope are now level. Carefully re-tighten the scope rings to the manufacturers torque recommendations. Then the scope should operate properly.

I would check your pellets.

Light pellets typically perform horrible in break barrel rifles due to their tendancy to fly around

Make sure you have a stiff, tight fitting pellet. Smaller soft pellets also will contribute to accuracy issues as they deform much and can let air escape from around the skirt when fired (called "blo by")