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Power is good but accuracy is king.
For a spring gun you really need a target grade weapon which cost about $1000 new. Recognised brands are Air Arms Tx200 and Weihrauch. In principle an underlever...

For air rifles equivalent ranges are 1/10 of using a centerfire. Eg a 20m shot is comparable to a 200m shot with a 308.
With spring guns you need to head shoot so its whatever distance you can put...