Guns are only able to hold a certain amount of ammunition. Once one has fired the gun one bullet has left the chamber. Once all of the ammunition is gone, one will need to reload the gun in order to fire off more ammunition. If ammunition is not reloaded, then the gun will make a noise, but nothing will happen.
Sorry, but we need more information on the term "round barrel gun".
To reload your gun in the game simply press 'r'. So easy a caveman can do it.
there is a button at the top of the screen that says reload click it to reload
When th ammo in the sentry gun reaches 0, then you can reload it. To reload, walk on top of the sentry gun and press the F key. I'm not sure if you can reload it when there is still ammo in it though, but you can try. When you reach the rank Colonel, once you set up a sentry gun, you will have double ammo for the sentry gun, and you can reload it faster.
shoot outsid the screen that should reload your gun.
when you are in the pea-shooting contest and you need to reload, there is a big bullseye that has RELOAD across the front of it in the middle-upper screen,next to where it shows how many peas you have left. Hope it helps!:)
Chamber
you have to get the USP pistol and empty the clip and when you reload it will "flip" the gun
default is R. goto options keyboard and look for reload key
you cant
space bar
Yes, the operator does it.