Scope issues

Usually the first thing I do when I get a new scope is to optically center the cross hairs or IOW to put the cross hairs in the center of it's adjustability range. You can do this by counting the clicks on the windage and elevation and dividing it by 2. If you have 200 clicks of windage put the windage at 100 clicks in the center. Same for the elevation. Or you can try the mirror method, usually works best of you have an illuminated reticle.

Then I would take the No Limit mounts and adjust them to where your zero ( 25, 40,50,60 yards) would be very close to your desired zero distance. Fine tune it from there with the windage and elevation turrets. The closer you get to the outer limits of your elevation and windage maximums, the more stress you put on the scope internals. 

It is also possible to torque down your mounts too much and actually dent your scope tube which could stop you from being able to adjust the windage and elevation properly.

There are videos on YouTube about how to do all this. Tom Cat Airguns or Airguns 101 has some very well done videos on his web site.

Hope this helps

Shalom 

John
 
Or if you want to take advantage of all available turret travel there is another way to do it. But doing this has compromises like a decrease in image quality and/or loss of the full FOV/ due to vignetting.

I zero at 30Y. Using a new, as well as a "large" paper target.

Next is positioning the no limits mounts all the way down in the front and all the way up in the rear and slightly tighten the screws on the rings/mount that allow the up and down movement.

Then bottom out the elevation turret on the scope and fire a shot on paper. 

Now comes the trial and error thing. loosen both the mentioned screws leaving the front of the mount bottomed out and adjust the rear mount down a tad, it's not a bad idea to use a automotive type spark plug gap feeler gauge to measure how much you have moved the mount.

Keep repeating the above until you get within a few mils, or 6-7 moa, high of POA. Now adjust the turrets on the scope up that same amount. Tighten all the mount screws tight, tighter than you would normally but not to the point of stripping them. 

At this point just zero the rifle/scope like normal and set both turrets to 0.

By having the turrets not totally bottomed out, but still close to it, you'll have most of the total internal travel of the turrets to dial up to use for long range, and usually the image quality is acceptable, as well as having the full FOV in the scope. 

I did it this way with my no limits mount and IIRC my scope has 19 mils I can dial up to so almost 4 revolutions, which can get me to 230 yards using my 25 cal FX Impact.




 
I'm sure that scope can and will give you up to and beyond 100 yard zeros … I mean … well … that IS why you bought the No limit mounts, isn't it? But I would definitely optically center that scope before anything else. Once it is optically entered, simply adjust the mounts to distance you want for zero. Or you can try what Steve said to really sling that pellet out there and touch something. 

The truth is that unless you know that the reticle is centered in the scope, you have no idea where it is right now. Someone at the factory might have been playing with it and twisted the elevation turret … I've bought scopes that were so far off as to make them unusable before I even put them in the mounts. That's why it ALWAYS pays to do that first, then you will be starting from where you need to be to make adjustments to your No Limits. Those mounts are good … use them like they are supposed to be used. There are videos all over YouTube to help you. There are even videos on the No Limit mounts themselves.

Just a word of advice about torqueing down the mount screws. It doesn't take much to put a dent in that tube. If you dent the tube, you can block the internal gears in the scope from being able to adjust the scope … plus if you need to send the scope back, it may well invalidate your warranty as most scope manufacturers consider that as abuse. When tightening down the screws on the mount, never torque it down more than you can turn it with the short end of the allen wrench. 

Shalom

John
 
Steve and John are both providing good advice. If you haven't done any adjustments to the No Limit mounts its possible they are tilted in the wrong direction which would drastically impact your ability to zero very far out. Barrel droop is more of a problem on break barrels than it would be on a Boss, although it's possible. In any case you should have plenty of adjustment available in the mounts to zero at a hundred and then dial up to significantly farther than that. With my 25 cal RAW with Sportsmatch adjustable rings I have found that zeroing at 35 yards is ideal because at that zero I never have to dial the scope turret down even for short range work so I can set the zero stop on the 35 yard zero and just dial up from there to whatever my target distance is. Your math may be different depending on what pellets you are shooting and how fast you are shooting them. My RAW is tuned for 40 foot lbs (JSB 25.39 gr @ 850 fps)

I start with my vertical elevation turret about one full rotation off of the bottom and then get very close to the 35 yard zero by adjusting the mounts. That leaves me plenty of upward vertical adjustment and it has worked very well for many years.