My first real air rifle was a Feinwerkbau 124/127 .177 cal delivering about 1000fps. Bought it in 1975, thought the price was outrageous at $125. It's a barrel cocking sporter. I had a Williams receiver sight on it at one time, but later added an air rifle scope. It's more accurate than I am for serious shooting. The jerky feeling when the spring releases is unnerving at first but you can get used to it. I have made kills on birds at about 40 yards, but that's been a long time ago.
My second and last is a Feinwerkbau 300, a recoilless match rifle with diopter sights. It is a side lever cocker,still a spring air type, but when you pull the trigger as the spring releases, a catch releases the whole barrel cylinder spring assembly , which slides back a couple of inches on rails, thus counterbalencing the feel of the recoil from the spring piston. Velocity is not nearly as high as the sporter, as it is designed for optimun accuracy at 10 meters for match shooting, but at the time I purchased it in 1987 , was still higher than some really cheap air rifles. Accuracy at 10 meters is supposed to be something like 0.03" center to center if you are good enough.
They are fun and still much less expensive to shoot than a .22, plus quiteness is a big factor. When my son was born I was in base housing while in USAF, in a duplex, and I used to shoot from the room where he was sleeping down a hall into another bedroom where I had my backstop without awakening him.
I have not shot them in several years, guess I should get them out and do a bit. One thing, with the high powered spring air guns is that you must use a special silicon base oil to lubricate the cylinder/piston. Pressures are so high that common petroleum based oils will ignite like in a diesel engine, often damaging the piston seals and sometimes blowing pellets apart.