I get a lot of questions about using standard caliber (.22 and .25) Airguns for long range pest control. In this context, long range means 75 to 125 yards, and the viability is dependent on three primary variables: environmental conditions, the gun, and the ammunition. If everything lines up, you can get impressive results on prairie dogs, ground squirrels, Eurasian doves, and other smaller species that are out there a ways.
Conditions includes things such as wind, rain, shooting up or down hill, intensity and direction of sun, shooting position and rest (shooting off a portable bench, sticks, sitting, prone). A a rule, if you have anything more than a wind of a couple mile per hour, you’ll need to pull it in. The other thing you need to understand, is that the wind where you are is not necessarily the same as the wind where your game is. So besides looking at indicators at the muzzle, you need to look for those along the path and at the termination point.
You need to make sure that you have a stable rest and shooting position, the gun has to be rock solid and so do you. In my experience the most stable position is shooting prone with the gun rested on an attached bipod or resented on a bag. However, this position is often not possible, because you need to shoot over grass, brush, or rocks. The next best is off a portable Benchrest, but again this is not always practical, especially when you need to move a lot. The way I often end up shooting is sitting with the gun on a bipod or tripod, and to fortify my position I’ll try to find a backrest I can lean against.
The gun of course needs to be capable of shooting tight groups, and higher velocities with a heavy projectile is preferable. I have found guns in the 35 to 70 fpe range tend to work well for reaching out. I don’t mind a single shot rifle for this application as you tend to have time to reload and you are most frequently shooting in warmer climes. A heavier gun is easier to stabilize, but I haven’t necessarily found that the rifle needs to have a long barrel.
Pellets that I tend to use for longer range shooting are round nose and heavy. These are generally more accurate, they retain energy better, and produce a good terminal effect on quarry. Heavier pellets are a bit less susceptivity to wind, but still if the winds start blowing, dial it in.
Some of the guns I have had good results with are the FX Royale, the FX Verminator, the Daystate Air Ranger, and on the less expensive end I have even had good results with the Benjamin Marauder out of the box. The thing is you need to put the gun, scope, pellet, and shooting technique into practice on a regular basis, and understand how and where it shoots at increments across the range you’ll be shooting. Fill out a card that maps the POI at 10 yard increments, because this can have a major impact on your success as a long range varmint sniper.
The last thing I’d recommend is advice I am unable to follow myself, pick one gun and use that one gun. As your familiarity with your rig increases, so does your effectiveness. If you use this advice, you’ll be able to shoot varmint out to 100 yards ethically and efficiently!