Vuurwapen Blog has done every AR-15 shooter a service by creating the AR-15 Weight Calculator. This easy to use tool allows shooters to determine what a potential build will weigh by entering the planned components into the calculator. It is quite accurate and there is already enough data that, even if your specific component isn’t listed, there is something close enough to get you into the ballpark.
This is a very useful page.
Great tool… I coined a phrase a couple of years ago (at least I think I was the first) regarding the tendency of some AR owners to over indulge their accessory rails, “How much can you hang on to a gun before you can’t hang on to a gun?”