..definitely allowed both in open or production optics...only slight advantage to someone NOT used to a red dot would be to co-witness and get used to seeing and acquiring the red dot, or thinking he needs iron sights as backup if the red dot fails (battery goes dead etc), BUT case in point: if they were very beneficial you would see both iron sights with red dots on open guns, you don't, the iron sights when using a red dot are just not necessary or beneficial and if anything a detriment as they can be a distraction
