I believe wad stan is trying to imply is just simply zeroing. There's no reset for zeroing, unless mayb if the weapon is electronic (correct me if i'm wrong, bcos as far as i know i nvr ever heard of any resetting switch for sighting equipment)
So you dn reset the zeroing on the air rifle or air pistol. Technically speaking, it's not about zeroing the weapon. Rather it's zeroing the rear sight on the weapon. (but to make things easier to say, it's zeroing the weapon. LOL.) So if a certain sighting is obtained when shooting a grouping with a shared weapon, the shooter shld simply just zero the sighting to the centre of the target.
Let's give an easy example between two shooters who know each other and share the same weapon. Both of them can easily zero their weapon to their own requirements. All they have to take note of is, what is the number of clicks in terms of height and lateral difference, i.e. Elevation & Windage. Sounds easy by just remembering the difference, doesnt it? It gets more complicated as the number of shooters using the same weapon. So do the math yourself! Haha.
And don't worry about asking questions. Don't even start thinking if it's noob or not. Everyone starts off somewhere and it's how they learn and get better. =)
Cheers!
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Yours truly. the Flamin' Phoenix. ALWAYS