Being new to this game I have a few questions

So I know what I sould be acheiving on a rabbit shoot coming up in a month or so using the .223
How far are you average and long distance shots?
Are you using a range finder or do you just get used to distances after the first couple of dozen kills
55 grain projectiles are the busines or are you using really powered up light projectiles, still talking .223 here?
Being a dirty foreigner, I've never seen a ground hog. Are they a bit smaller than a rabbit? Here in NZ we have rabbits and hares.