As with most things it's horses for courses... plenty of situations where .22 RF unsuitable for the "rural" but basically overpopulated nooks of Surrey (most due to ricochet), but FAC air is fine. I would say however that I see little point in more that around 30 FP for air (I ran mine around 28) or it just becomes too noisy and air hungry - and 900-950 fps with a .22 pellet will flatten the trajectory a far as possible before things get unstable. Even with a midweight .22 (say 16 or 18 grain JSB), that more than enough to take any quarry at the ranges imposed by a subsonic trajectory. The same fps with a 21 grain magnum will have no useful affect on the end result (unless you are shooting in a gale), and make a lot more noise as it'll need an extra 10 FP.
I also ran my .25 ELi at "just" 20 FP with 20 grain H&Ns, and it was a brilliant squizzer gun. Don't fancy taking squizzers with a rimmy.
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.