I just got a new M&P15, but haven't had the chance to shoot it yet. My question is this, It came with the detachable carry handle and fixed front sight. I grabbed a Tru-Gold for it but want to know it the is anything that I can mount to the carry handle? This way, if the battery goes dead, I can still use the mounted sights on the gun. Or would you suggest purchasing new rear sights and use both. If that's the case, will the be any issues changing the rear sight from height of the carry handle to the lower flip down sight.