I've been thinking of replacing my air rifle scope with a better quality model and see that the state of practice is to use high magnification scopes with adjustable objectives. Why is that? My scope is a fixed 4x scope and it's fine for anything I want to do with it. I can't understand why anyone would want more magnification unless it was for some special purpose like shooting very small targets within the effective range of an air rifle. Then there would be the question of rifle steadiness that would become a challenge.
Can you explain this to me?
As with almost any airgun related question the answer is, it depends.
For small critters (squirell, sparrow, etc.) out to 50 yards, I think a 12x to 16x magnification would be adequate to precisely aim at their small vitals area. Those same critters at closer ranges up to 30 yards could be accurately engaged with magnification of 4x to 8x.
For Field Target, Bench Resting and other types of airgun long range target shooting, higher magnification is in order to make it possible to engage such small targets and for accurate distance estimation in FT (as clearly explained by Dave). For fixed distances shorter range (30 yards or less) target shooting and plinking, lower magnification may be better, but this will always depend on the shooter's taste for scopes.
Scopes are nice but I perfer aperture sights for right now, just hard to find a good selection of aperture sights for air rifles and Mendoza may be the exception .
Aperture sights have the advantage of being more resistant than scopes to the punishment of magnum springers. They are also better suited for short range off-hand shooting, and the best allowable sights for 10 meter air rifle match shooting (my favorite). There are some very fine aperture sights available, the problem is they are even more expensive than many scopes.