The ORIGINAL Mini-Scout-Mount 14 fits every serial number range manufactured prior to 2007 - serial numbers starting with 1 (before the 580 Series), including Ranch Rifles & the AC556. See our other listings on Amazon for newer rifles (580 series +). How does the mount work ? It replaces the upper hand guard. Remove the mount, put the hand guard back, and back to the original rifle! Does it affect the accuracy ? Yes, in a good way. The design has the effect of trussing the barrel by the gas block the mount clamp. There is a V-block machined into the underside of the mount body where the barrel rests. This V-block centers the mount body directly over the center of the rifle barrel. When the barrel clamp is secured, the rifle barrel cannot move out of this V-block. I have an aftermarket stock, will it fit ? Yes. Can I still use my factory iron sights with your mount installed ? Yes. Are the holes on the sides of the mount for installation ? No. Add our Tactical Light Mount Kit rail to attach a flashlight or laser. I have an after-market heavy barrel installed, will the mount fit ? ONLY if you are still using a factory lower gas block assembly. If you have a different gas block, it will not fit. I have a side-folding Ruger factory stock, will it fit ? Yes, but if you have the forward sling swivel mounted on the side of the gas block, you will need to order the GB Model for side-folding stock. I have a AC556, will it fit ? Yes, but if you have the Ruger factory folding stock with the forward sling swivel mounted on the side of the gas block, you will need to order the “GB Model".