The O-ring engagement was among a few of HK's innovations with the USP line of pistols. They claim it provides better accuracy by allowing the barrel to fully lock up with the slide. There is some debate to the validity of the claim, but nonetheless,… more »

If you want to shoot suppressed, the first thing you may notice is that your sights are probably blocked by huge can sitting at the end of your barrel. Read more to see how you can fix this problem. more »