All I know about the HKs I learned from Call of Duty... and my vast experience is you better get a head shot for a guaranteed kill!:devil:
You're going to love the MKII. They are so fun, and so cheap to shoot it should be illegal. Wonderfully accurate. I finally took the optics off mine because it wasn't a challenge at the ranges I shoot! It just wasn't fair. The MKIII brought some, let's say, Lawyer inspired changes that didn't make it a better gun.
Field stripping the Ruger is not as bad as folks say. Just remember it's all about the Hammer, flat to take the bolt off, forward to put the mainspring unit back in, and Keep the trigger pulled, when levering the spring. It might not make sense as I've written it here, but when you're reassembling it, it will.