Harry, yes Sir, it will install on you top Picatinny Rail no issue. It will also co-witness with your Flip Up Sights as well. Cheers and stay safe!

It will work but that Red dot is kind of big and bulky and for that price you could get
A Holosun HS403A, Vortex Sparc AR ( vortex has unconditional lifetime warranty), Primary Arms Advanced Micro Dot, Or a Sig Romeo5 are all options that are on the same price range ( in most cases are cheaper) and give you a lighter package and proven performance, and better battery life

This scope will WORK for your firearm. The mounting system this sight comes with will make installation a breeze on your Radical 556. Remember, any Picatinny mount scope will work on Radical 556 or other AR15. I hope this helps