Albert, you are talking about the
maximum elevation adjustment, right?
I just looked over my Scope Specs Tables of about 150 scopes — magnifications 3-12x — 4-16x — 6-24x — 5-30x — that are airgun suitable (10y min. parallax, holdoff reticle, exposed turrets, $500 and under):
40MOA : there are very few black sheep that only have 40
50MOA : there are some that only have 50
60MOA : this is a very common value, and on the lower end
70MOA : this is middle field
80MOA : this is a common value, at the upper end.
90, 100, 110MOA : these are exceptionally high values, but can be found!
The max. elevation adjustment spec is only important if you are going to dial your turrets.
If your gun's barrel is pretty straight (not a drooper), you'll probably end up zeroing your scope at around the optical center of the scope.
➔ That provides the
best clarity of the scope image.
➔ But it also reduces the amount of elevation adjustment that you have available. E.g.: On a scope with 60MOA max. adjustment you only have 30MOA to dial up, and it seems there is some consensus to not dial your scope all the way to the extremes up or down (unless it's a scope for a 4-digit dollar amount). So, you might have about 20MOA usable.
Now, are 20MOA "ENOUGH"? Well, you could
take a ballistic calculator, type in your probable zero, and your
longest range with your
heaviest pellet you anticipate to use.
Then calculate and see
how many moa (or mil) you need to reach out to that range. If you need more than 20MOA ➔
➔ Get adjustable scope rings, or a canted scope rail, and make use of the bottom part of your elevation adjustment range...!
You really need to make those prognostic calculations with a ballistic calculator if you want to know how much elevation adjustment you'll need.
However, if you're just planning of
shooting out to max. 50y, and with
at least 15FPE (.22cal), you should be fine with
50 or 60MOA.
If you want to reach out further, or use a gun with much less power, you probably will need more elevation adjustment, or adjustable rings, or both!
Hope this helps some!
Matthias