Nobody's going to answer your original question. It's been asked a million times, and everyone hates it.
As for the handguard rail, there are so many to choose from that you should just pick the you like personally.
By handguard ring are you talking about the delta ring? If the problem is incompetence and not that something broke, just get an optic so you don't have to use broken iron sights.
Guardians of Asgaard - KF32
VFC H&K 416C
VFC KAC SR16 JL Billet SBR
TM FN Five-seveN