I used my Oly Arms M4 to kill a wild hog in southern Ohio a few weeks ago and it did the job quickly and cleanly. I'd never hunted with the M4 before, and I was pretty impressed with it's performance for a rifle that shoots "a good woodchuck round", as I've heard it described...
I had an Oly back in the mid 1980s. This is when they built them from junked parts and it was crap. It keyholed half the rounds I fired.
Since they have gotten serious about building them the quality has increased.