I just bought my first glock (a glock 27) used a few weeks ago. The first time I took it out I had 8 fail to fires inside of 250 rounds. I took it out again last weekend and put another 200 rounds through it. I had one more failure that time. I took it to a local glock certified gunsmith and he told me that it's shooting out of battery. He also told me that there was nothing he could do about it and that besides the occasional fail to fire that I shouldn't have any other problems. What should I do from here? Is this gun even safe to keep shooting?