I think around 600 with that red dot. I don't expect it to last forever but I'm impressed with the performance so far, if it stops working I will just get another one. At $20 including shipping I will not lose any sleep over it.How many rounds has it seen? It'll be much more telling a 1000 or so.
When the barrel gets hot it gets hot, nothing else happens.What happens when the barrel gets hot?
I dunno...why not just get a cheap reciever cover with a rail or a gas tube with a rail