Optics are required in all situations, and especially in CQB shooting.
We need to design indiv weapons to solve the 90% problem, which is quick encounters at 100m or less. The C7A1 at present is the solution to 10% of the soldier's problems, ie deliberate shooting at ranges from 200-300m which it is what it is optimized for.
Irons absolutely do not always work, they can get smashed and lose zero as well. And putting damage aside, they are "broken" for over half the day by virtue of being unusable. There have been no widespread issues with the failure of optics in OIF and OEF, and we're talking tens of thousands of units in daily use. Battery life and fragility were long ago shown not to be the boogey man the optic sight detractors said they were going to be.
Irons start off being useless at least half the time, and have severe employment limitations to boot. They are obsolete, and not sufficient as a primary sight.
Has anyone here actually made use of an Aimpoint or ACOG in the field or for other shooting? Can you really form an objective and educated opinion as to their necessity, durability and other advantages without having done so?
You have an excellent point as to the necessity to use irons in a back up role, one I overlooked in my dogged instance that optics are necessary - I think you're absolutely correct. What I don't have is much worry about optics going down. It simply hasn't proven to be the case.
There's a great paper
HERE that pretty much covers all the reasons I can think of why irons alone don't cut it. There's another great paper on combat marksmanship skills
HERE.
A description of what a Marine Gunner is can be found
HERE. I only wish we had such beasts in the CF - to me Gunner Eby's papers epitomize what a Senior NCO should be doing; namely being incredibly well versed and proficient in the technical aspects of soldiering, and ensuring everyone else is made aware and brought up to date too. The methodicalness of his thinking is visible - he precisely identifies what capabilities a soldier and his rifle must have, and thus what training and equipment they need. Quite the logical and refreshing change.