My shooting buddy has the Colt M4. I have NEVER seen a gun that fails to fire like this one. I'd say about 1/4 the rounds (much more on a bad day, less on a good) fail to fire with it. He's sent it back, and had a gunsmith work on it, and it's a bit better now, but when I started looking for a .22, I knew that was one I would completely ignore. He bought a new HK, and is pleased enough that he never takes the Colt shooting any more. But I personally much prefer the S&W to the HK. He even said he'd shot a 15-22 years ago, and it shot flawlessly. Don't know what's kept him from buying one.