I bought my first one at a flea market in the early 1980's it was a 4.5mm/.177" model B-3 that has a fixed barrel with the cocking lever under the barrel. Used it to slay 1000's of pidgens,starlings,and sparrows. It fired Crossman 8.2 grain pellets at 630fps which was around 100fps faster than the top of the line Crossman and Dasiy multi pump rifles. After about 10 years it started loosing velosity so I rebuilt it by putting a new spring and making a new piston seal. This resulted in it returning to it former preformance level.
Since buying the first one I have owned a dozen different models of Chinese air rifles. I have owned several models of under lever,side lever,break barrel,and CO2 models. I have shot just about every model they make except the high end target models.
Velosities listed below are with stardard weight Crossman pellets.
The lower priced break barrel rifles are pretty much for kids plinking in the backyard due to it's low veloisity of 320fps in .22 and 430fps in .177.
The under lever and side lever models produce low-mid 600fps velosities and are real good for 100-150 feet shots at small game(sparrows,starlings). Hunting big game(pidgens,squirrels) require 100 feet or less distances with head shots to put them down with one shot.
The top of the line rifles rated at 1000fps will only produce lower-mid 800fps velosities but do increse the distance for head shots and allow chest shots at closer distances on big game with clean kills.
In the mid 1980's I bought a RWS model 36 rifle which at the time was the top velosity model rated at 1000fps. It would produce within a few fps of the rated 1000fps velosities and really incresed the distance for clean kills on big game.
Bottom line is the Chinese air rifles are the best bang for the buck. Just make sure to pick the right model for your intended use.
Low priced=plinking only
Mid priced=short-mid range hunting.
High priced= long range hunting