Treebloke you have obviously been looking for a solution which is good, but i dont believe the RSPCA actually recommend
any method for amateurs
killing anything.. i think the general position is utilise someone who has the skills and equippment already..ie pest control, deer stalker etc etc.
Personally spring traps, if set properly and safely, with the target species in mind are approved
methods in law...and for a reason... because dealing with a live trap is an issue..
The higher powered air rifles require a licence and are up to the job, likewise a limited number of pistols but still its no good shooting it blindly in the front of the head. I have seen a comb
which sldes into the top of a live cage and thus restricts the squirrels movements to a smaller area allowing for a cleaner shot.. i doubt it would take much to make a simple version.
kittens
pets..Hmmm to a lot of people cats/kittens are a pest to (vermin) and many country folk
used to drown them to...now we are smarter and have better options so few do.
Yes i do have a lot of experience, and being a firearms trainer amongst other things i have more options available... but at the end of the day..you cant get passed the basic thought that if you want to kill something , make sure you know how and what to use before you catch it.
Currently i use a shotgun, i use it from the right range and only shoot when i am 100% sure of a kill.... as to Darrens question on live traps... if i can remove a squirrel by hand from a cage , getting a safe and clean shot with an air gun of sufficient power and accuracy is not an issue.