Re: "adult" air rifle
I've been shooting air rifles for more than 30 years and they definitely have their uses. Within their effective range, they are very accurate. However, spring Piston air rifles are VERY hold sensitive, but are accurate if you do your part and can teach one a lot about ballistics....
I started with a Daisy model 94 BB gun in the late 60's (used it so much the receiver broke) and I killed more than 400 starlings and blackbirds at home with it (my job was to keep them out of the garden and the fruit trees). Learned a lot about stalking, patience, hold-over, etc. with it. I remember I could see the BB's in the air. Most of the starlings were taken at less than 15 yards.
Saved my money and moved up to a Beeman HW30S in 1975 or so and couldn't believe the accuracy-it was a lot faster than the Daisy was, although at around 650 fps not really speedy either, but I did kill a crow with it at 27 yards (head shot). I graduated to an Beeman R8 in '83, had to replace the mainspring with it twice, and now has over 14,500 pellets through it. It's around 780 fps and pellets would go through a squirrel at 20 yards or less.
Now my go to air rifle is an Air Arms TX200 in .177 (around 950 fps with 8 grain pellets). Boringly accurate. Shots at 30 yards or less are easy. I've taken starlings as far as 64 yards with it ('bout all I can get distance wise without creating neighbor issues) and my hold was around an 1-1/2" to the right because of wind that day. Taken both squirrels and rabbits, but keep those shots at 35 yards or less just to be sure it is humane.
For power, I'd love to get a Theoben Eliminator (Beeman Crow Magnum) in .22 - it's about 850 fps with 14-15 grain pellets. It is a gas ram, rather than spring piston. Have a friend with one and it's a great shooter. BUT here's a caution ....the more powerful, the harder to cock. The Theoben takes around 50 pounds of force to cock. Doesn't sound like much, but do it for a number of shots and it adds up quickly!
Oh, if you look at the velocities people are getting in real life with the RWS 460, it's also around 800-850 with 12-14 grain pellets.
Here's a test of the RWS 460 It is advertised to have 36 pounds of cocking effort required.
I am considering one of the new "nitro piston" air rifles to try them out...if you check out Pyramid Air's website, you can get them from Crosman, Benjamin, even Gamo, and have some pretty good velocities.
For more velocity, you'll have to go to the Pre-charged air rifles.
Just my two cents worth.
