Never had to re zero after cleaning ,check zero with every batch of ammo or if the rifle has taken a knock .I bought a new rifle this year ,put a couple of patches through just to check it was clean ,put half a dozen rounds through to see where it was on the target ,let it cool , cleaned ,got it on the money , cool , clean , few more rounds to check i was happy with it ,cleaned it when i got home , shot a fallow doe the next day .In saying this i must add my great shooting mate has cleaned his .22 about twice in its life & it seems to make no differance , i shot it the other month & it