You will never get irons that are faster than RDs. I really like carry handles and I tried to run one as my primary for awhile and it just isn't as effective as optics. If you are using irons, you must somewhat focus on the front sight post (as you are taught) and, for me at least, takes away some of my focus on my surroundings. With something like an EOTech or aimpoint, you can focus out on what you are looking at and the reticle is projected out on your target. I have found that if I try to focus on the target with irons, the post blurs significantly. I would think that at close range, you can definitely be quick with irons but due to the way they must be lined up, there is a much smaller margin of error when it comes to bringing your rifle up to your line of sight (and it will never be as fast as you could be with an optic). If my optic goes down in an HD type situation, I wouldn't even deploy the rear sight... i'd put the FSP in the middle of the window (absolute cowitness) and simply use the front sight.