I think the correct word you are asking about is "refurbished".
This is a common practice whereby a company will take returned items (for guns, this is usually some sort of police department trade-in) and rework them to the point where they meet original build specifications. This means replacing worn parts where necessary as well as refinishing the firearm.
US Laws do not allow these items to be called New, so the term "refurbished" or "refurb" for short is given to these items.
I have no problems with using refurbished firearms. This has been common with Glock, H&K and other firearms companies.