Just like new
There are a lot of Police trade ins and used firearms out there that can be purchased and 30%-40% below what NEW prices are. There are a few online FFL dealers that pick up the police issued Glocks and Sigs and resell them for under $400. I picked up a few that had a lot of holster wear but once I opened the action, they were hardly fired and they ran flawlessy. Most of the time this is the type of condition most Police trade ins are found.
Some firearms may have actually been shot a lot, but if you think the accuracy in your Glock is starting to deteriorate, if you got it at a good price in the first place, replacing the barrel is easy and not a headache. Most of the type a barrel will just drop right in. Glock Barrels can be found for under $200 and will last longer than most shooters will ever know.
Things like recoil springs and firing pins are pretty much a MUST for serious shooters because sometimes it’s not always the guns fault that something wears out or breaks. Sometimes bad ammo can wear out a firing pin faster than normal and recoil springs are going to wear out at some point. The 2nd recommendation I would have would be to store magazine springs and followers. Those will wear out, not as often, but as often as recoil springs. If you’re a plinker and occassion shooter, these won’t be necessary, but if you put a couple thousand rounds through your Glock every year, something is going to wear down at some point so it’s best to have the spare parts around when it happens.
GLOCK MAGAZINES
It is exactly these characteristics that meet the requirements of police, special units, security services and the military. Extremely tough tests by public law enforcement agencies prove time and time again that GLOCK “Safe Action” pistols function without compromise, even under the most extreme conditions.