It was stupid and I was taking a chance, but I started carrying my Glock 22 before I ever fired a single round through it. I had no idea whether it would actually shoot or not. I carried it for about three days before I was able to get to the range with it. My first range trip I put about 500 rounds of various types and brands of ammo through it without a single hiccup. My second trip to the range was about 300 rounds of my chosen carry ammo.
Now, I wouldn't normally recommend doing it this way, but at the time it was my ONLY handgun. I decided that carrying an unproven gun was still better than not carrying anything at all.
I have since fired several thousand rounds through it without a single problem.