I served in the German military when the standard issue rifle was the Heckler & Koch G3. I was a light infantry grunt and (later) a drill instructor at boot camp, which is why I feel qualified to make the comments that follow.
Every single G3 pattern rifle with H&K diopter-style sights I see at American gun shops and gun shows has its sights set to the 100-meter “v-notch” setting. THIS IS WRONG. The 100-meter v-notch sight has only three purposes:
- Anti-aircraft fire on the full-auto setting
- “Sturmschiessen” (suppressive full-auto fire)
- Low-light shooting where the diopter sight is useless.
Note that two out of those three purposes require a full-auto sear, which makes them inapplicable to semi-auto HK91s and -93s.
Outside of those rare circumstances, the drum sight of a G3-pattern rifle is to be set to the 200-meter diopter setting as the default. Failure to do so will earn you the disapproval of any former Bundeswehr drill sergeants present, who will at the very least turn your sight setting to the proper one.