You'll like that 7mm-08, my brother has had one for 20 years or so...Of course he still has a long ways to go to kill as many as I have with my .243...

Buy a .243, use it during the summer for crows, coyotes, groundhogs and other varmits and you won't have to worry about this "margin"...You'll learn to hit what you shoot at...I've even taken care of a few bears eating my peanuts with the dang thing...

On the barrel...Funny how we are, I rebarreled mine a few years ago and went from a 22 inch to a 24 inch...With a short action, a 24 inch is about the same overall length as a 22 inch long action...Anything less than 22 seems too dang short for me...