What type of sighting system did the M1 Carbine first use for varying ranges?

The M1 Carbine was designed with a peep sight, which is a type of rear sight that features a small aperture. This design allows for greater accuracy when shooting at varying distances, as it helps to align the shooter's eye with the front sight and target more effectively. The peep sight provides a clearer view of the target and reduces the effects of focusing on the front sight, making it easier to maintain sight alignment.

In military applications, where quick target acquisition and adaptability are essential, the peep sight accommodates different ranges by allowing the shooter to make rapid adjustments. The M1 Carbine's peep sight was a significant factor in its effectiveness as a lightweight semi-automatic firearm that soldiers could use in various combat scenarios.