Hey there! I just picked up my second gun, an M&P 15OR. Last year I bought an M&P 15-22 for my first gun and was hooked. I decked out the 15-22 but after firing a friend's Sig M400 I knew I needed a .223/5.56 slinger. I have a couple of TRUGLO red dots so I put one on it but I don't know how well they will hold zero. Any suggestions for a reasonably priced red dot? I was considering a Sightmark Ultra Shot QD but have read mixed reviews.