I'm looking at a 6.8 SPC upper for my AR. Do I need to change the recoil spring and buffer? How accurate is the round? I'm looking to use it for target and maybe for pigs and predators. The area I hunt has a lot of Coyotes and Bobcats. I've been using my 17HMR and a couple of .223s, these are OK but a heavier/bigger bullet can't hurt (me anyway). From what I have read the ballistics are between a .243 and a 7mm-08, I'd think that's good for the small White tails and average size pigs I hunt.