Have the Quest Extreme II (.308)
Mine has worked very well without any problems. At least one other poster has had headspacing problems with his QEII. Have not had that problem with mine and it has functioned perfectly for me. With open sights, my best 5 round group off hand was 3" at ~65yds. I was having trouble shooting off the bench that day and that is why I was shooting off hand. Other groups ranged up to 6" or 8" (can't remember definitely, I'll have to search for the short write up I did) using different holding techniques. I recently put a scope mount on mine but have yet to zero and group it. I had intended to do it today but BROUGHT THE WRONG DANG RIFLE! Had my R1 FAL instead of the QEII.
The rifle came with a steel scope mount but it was crap. Had to do some serious grinding to get it to fit right and even then, it came partially off after the first round. Threw it away and bought a B-Square from Midway. (Cheaper than buying direct from B-Square.) Seems to be very solid on the gun. Easy to bolt on, no gunsmithing or minor grinding. Have a very cheap 3-9X40 BEC on it. The eye relief is poor but it will do to get groups until I can get a better scope. (I chose BEC because of the price, IIRC $60, and variable range, and I've never tried them before. Made in China, purchase before the P-3 incident, lifetime warranty but probably is not worth the postage for repair/replacement. We'll see.)