1. make sentries
2. name sentries
3. make a point_template and name it
4. add all sentries to template
5. create logic_timer
6. set time to a refire interval, mine is set to 30 seconds.
7. set output to KILL sentries
8. make another output a split second or more later to make the point_template frocespawn
I am a bad person, please attack me with various Owl-related insults.
I'm at work atm but I have a map at home got it online from a server, can't remember the name - I'll post it because I think it has what you are looking for - you'd have to decompile it to see how it works but it works like this(perhaps some of you have played it):
round start gun exists - you run to poin x utility type door opens up exposing a L1 sentry gun - it attaches to you you get an engy to upgrade it and then you run around with this gun shooting up the oopsing team - if you or the gun die then it respawns back at the cabinet.