Originally Posted by Larry M
Stick a long screw or bolt (a couple inches or so) in the end first.
I also try to keep several, clean cartridge nozzles around. If the calk has set up in the nozzle, I have found I can unscrew the old one and sometimes (up to several months) the caulk in the tube is still good. You can also buy spare 3M nozzles but they're around $1-2 each.
That is what I found as well ... stick something into the nozzle long enough that reached into the tube for storage. Collect/buy new nozzles and the tube can be reused a few times over a period of few weeks. If you let the caulk in used nozzle cure, it does not stick to the plastic well and you can remove the caulk plug cleanly and reuse the nozzle.
After that, the partially hardened tube is still good for dipping the screws ... just drive them into the tube in soft spot and you can squeeze out more caulk.