Remember the AR already has a base built in unlike most bolt actions. Of course, you could make it work either way but they make mounts specifically for the AR that vary in height and have enough offset to get correct eye relief with most scopes. Unless you swap optics between AR's and bolt guns, the picatinny rail that's on your upper receiver is the only base you need, just get the correct mount.
For me, AR mounts with a 1.4" height (from top of receiver to center of scope) is about perfect.
