There are many reasons why you might want to buddy free float and art on your AR 15 rifle. The main reason is to increase the accuracy of the rifle. But installing a new rail on your rifle also gives you the opportunity to add a bunch of new accessories such as grips, lights, lasers, anything else the suit your fancy. To begin you’ll want to decide what rail you want. One of the more popular rails is a keymod rail. The keymod rail is very popular because it is very easy to add and remove mounting rails and other accessories due to the actual keys milled into the rail.
Many manufacturers are making attachments that are simply keymod attachments that require no mounting rail or other attachment device for attaching it to your rifle, which reduces weight and makes it easy to position. You won’t appreciate how easy the keymod rails are to use until you try some of the other free flow of rails. Please do not buy a quad rail, they’re very heavy and incredibly uncomfortable in your hand, so the first thing you’ll do is go out and put a bunch of pads on it to make it more comfortable which will add even more weight. Pony up the big bucks and get a keymod. When deciding which rail to get, a determining factor is what rail do you currently have, what gas block you currently have, and how long you want your rail to be. If you have a front sight post you’ll either need to get a shorter rail, or remove the front sight post and put a low profile gas block in. Removing a front sight post that is pinned in place is no easy feat and will require you to pound on your rifle harder than you ever wanted to. For many people building a new upper is a better way to go then to modify an upper with the front sight post. Once we have decided which rail and how long we want it, we can begin by removing the upper from the rifle. You want to make sure the rifle is unloaded, remove the bolt and place the upper in a vice. If your new rail requires a new barrel nut, begin by removing the flash hider. Once the flash hiders removed discard the crush washer as you’ll need a new one upon installation. You should now be able to remove your old rail, remove the gas block, and then remove the barrel nut. At this point you’ll want to get your new barrel nut, slide it over your barrel, and hand tighten it to your upper. Take your barrel nut wrench and attach a torque wrench to it and you’ll want to tighten to at least 30 foot-pounds and loosen several times to make sure your barrel is completely seated before you torque it down to spec. Once you’re certain that it is seated, torque the barrel nut down to at least 30 foot-pounds, and check for alignment of your gas tube channel. You’ll probably have to tighten up a little bit more in order to get the gas tube channel to line up, but you will not want to torque it over 90 foot-pounds. Spec is between 30 and 90 foot-pounds. Next you want to reinstall your gas tube. Try to line it back up with the marks previously there, you can test with compressed air to make sure it is correctly aligned. If any of these parts use screws make sure you’re using loctite. Once the gas block is on you can install the new rail. I’ll usually use a scope base and straddle the seam between the upper and the rail to ensure I install my rail in perfect alignment with my upper. Reinstall your flash hider and crush washer and visually align the center hole with the top of your gas block. At this point you ready to reassemble your AR and do a functions test, followed by a range test. Make sure for the range test that you use hearing and eye protection in case something should go wrong. At this point you can enjoy your new rifle and begin accessorizing.