Tell me about your Glock(s).....

[Mr. 16 gauge]

I'm looking for something to carry around water, and while looking at the plastic stock on my shotgun, the light bulb went on (it's only a 15 watt) and thought "What about a Glock?"
My experience with these guns is limited to my friends compact .45 ACP, which I sorta didn't care for, but there is a gun shop near my home that has handgun rentals, so "trying before buying" is definetly an option. Your thoughts? Any truth to the fact that they can't shoot cast bullets? Anything to look out for, like in police trade ins?
Thanks in advance...........