What all can be hunted using Air pistol & Precautions

That's around 3.17 foot pounds or shooting a 7.4gr Crosman Pointed at 439fps. A dove sized bird out to 25-30 yards max. A crow probably 15-20 yards max hitting him in the head. I headshot birds in a warehouse shooting a scoped Daisy 717 pistol at 360fps shooting 7.5gr Gamo match wadcutters up to 15 yards no problem. That's only 2.15fpe at the muzzle. Nothing but headshots instant death. Rats no problem body shots in head and vital areas.


 
If we are talking about a Uk legal limit air pistol I would only be comfortable taking rats, doves, and rabbits at relatively closer ranges, sub 20 yards with good placement. I have personally seen a crow eat a 20 gauge shotgun shell to the chest and still fly off a good distance, so anything but a headshot will likely just hurt the bird. Pistols in the sub 6fpe range are mostly for plinking. 
 
I would recommend 6 FPE to be sure and headshots only unless it’s small mice or house sparrows. I’ve just gotten a squirrel at 15 yards with 7 FPE to the head. For crow shot placement is everything, don’t do chest shot, I’ve dumped a 12 FPE 14.3 pellet square in a crows chest and it just flew off but I got one with a 7 FPE neck/upper vital shot. 
 
Have taken a few tree rats with a Crosman 2400 converted to hpa -

Depending on hammer spring adjustment, no problem getting enough power.

Rarely even try a shot further than 20 or so yards, and use any rest provided by nature when possible -

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I use this. A fully modified LP53 which puts 10 shots into an Inch at 15 yds.

The muzzle velocity is 525 fps with AA or Falcon 8 grain domes which retain at least 450 fps at this absolute max (for me) range.

At 10 yds it delivers a good 485 fps at the point of impact and easily shooting into a sub 3/4 inch group, making it a realistic proposition for hunting pests at short range.....I personally would not attempt such shots with anything less, having modified this pistol to fit the purpose and practised with it until a high level of marksmanship was attained.

As regard slack jawed PC types that might disapprove...I could care less, but try penetration through both sides of a rats skull the last time it was used on one at 8 paces. 


 
SteveV, I don't see a gauge setup on that pistol, how are you estimating in the charging of that?

Believe it or not up until around 25 years ago mostly all PCP guns didn't have manometers so you use the gauge on the tank or pump to fill and count your shots to know when it's time to refill. I have lots of old PCPs still without manometers.