A rental gun that has been not fired much
Find out what the date on the gun is and what constitutes as not fired much to the people at the gun shop. When I manged a range the gun that was shot the fewest was the 44 but that was about a box every few weeks.
On average the popular guns Glock 17, Sig P226, S&W 686 etc get rented almost daily with about 100 rounds through the semi's and 50 through the revolvers each time rented. Keep in mind Mon thru Thur its probably 200 and 50 but Fri thru Sun it can be 500 and 200. All in one week.
The S&W 340 PD, each range is somewhat different on the not as popular guns and what gets rented there. Hence asking them what they mean not much. Lets say they have had the gun 1 year and you can check this because they have to have it logged into their when the gun was processed into their shop.
So if they have it one year a one rental a month with 50 rounds thats 600 rounds. Not to mention that some of the workers may have shot a few boxes themselves through the gun. It is common that when a new gun is released that the workers will test it out to get a feel for it and see if they want it and to help them sell it.
I am calling BS on not fired much if they have had this gun more than 6 months. If it was not fired much why were the springs replaced and was it factory parts put in. I would recommend a new S&W 442, I am not a fan of the LCR but there have been many happy owners. Good Luck