The best options (IMHO) are going to be either a scout setup using a gas tube rail or an optic using the side rail. I prefer the side rail myself. The top cover rails/scope mounts are worthless junk. The PK series of combloc scopes are my preference. I have a PK-A, a PK-23-01 as well as a Cobra red dot sight and a few POSP and PSO scopes. All mounted on side rail mounts. I have had no problems and highly recommend this type of setup. Just make sure you get the right mount for your side rail type. Hope this helps.