JTD..... You have asked a couple of very pertinent questions and have had a couple of good, well thourhg out answers. I'm not going to try to compete with those answers except to make a suggestion.
If I was you, I'd put in a few keywords such as telescope, sniper...., you know the sort of thing into the forum search whatsit and start reading back. Very soon you'll be starting to hear what members are saying about this, that and the other PLUS what THEY have done and how they've succeeded - and sad to say, failed!
Go on, start reading and come back again with another ball park idea. Hopefully based on that other Enfield ball of fire, the No4!