When learning rifle marksmanship, is it better to do it with a scope or iron sights?
Iron sights develop marksmanship. They will highlight any mistakes you are making which is the reason advance marksmanship schools never start out on optics. Optics mask small errors that stand out when using irons. If you do not recognize your mistakes, you cannot fix the error.
The sniper’s use of iron sights serves mainly as a back-up system to his
optical sight. However, iron sights are an excellent means of training for the
sniper. The sniper is expected to be proficient in the use of iron sights before
he obtains formal sniper training and he must remain proficient.
There is a reason you train on iron before glass.
http://www.bits.de/NRANEU/others/amd-us-archive/FM3-05.222(03).pdf