Free: Contests & Raffles.
If used for hunting and not for close quarter CQB, then standard two point, hunting rifle style carry, will serve you fine.
I have tried several and settled on the Padded V-Tac (Viking Tactics) sling. Its comfortable for all day carry and is EXTREMELY fast to get on target. Watch the video on how to use it.http://vikingtactics.com/videos/pop-instr_video1_sling.html