Be careful with used guns on CL though, often times you get shady people selling non-working guns and only meeting in public places so you can't really test it.

If you can't test the gun, don't buy it.

I generally don't buy used guns on the classifieds anymore
I've run into problems that the seller tries to hide, like cracked receivers, their own shitty mechbox work, super glued hop up units etc

lot of the guns these days I've seen are marked down like a few dollars off the new price... claimed never gamed but they've plinked some ridiculous number of rounds through it... like plinking rounds don't use the gearbox at all or something...

Why risk getting a bum gun when for the few dollars more they've taken off you get something brand new?

with the exception of 1 gun I've bought off the classifieds, every one of them I've gotten required some amount of work or completely new major components.