I don't make claims, but I am very mechanically oriented.
Where do you go to school?
If you think you're mechanically inclined, put your money where your mouth is. Join a FIRST robotics team and build a robot to compete with 2500 other high school teams from around the world. Show us what you can do. Should be a simple competition for someone with your claimed abilities that's capable of designing a gun. My guess is you've never built anything from concept to completion.
I've been a FIRST mentor helping high school kids build robots for 6 years now. We've qualified for the World Championships 4 times, best finish was 12th. There are many aspects of mechanical design that you are not aware of just because you haven't been exposed to them. Being mechanically inclined doesn't necessarily mean you're able to design a mechanical system if you're incapable of learning and understanding the basic building blocks. Nothing wrong with being a great technician or gunsmith, but it's not the same thing as design engineering. Being able to take existing systems apart and put them back together again is a good way to learn what's out there.
The 3 minute video below shows this year's Mandeville High School robot, designed and built by a team of 10 high school kids. It finished 5th at the regional competition, didn't qualify for the World Championships since only the top 3 get to go. If you're really interested in learning mechanical system design skills in high school, there's no better way to do it. It's very difficult to find kids in America these days who do more than talk and fool around on the internet. Unfortunately, talk is cheap (especially when you don't know what you're talking about) and doesn't get the job done.
http://www.youtube.com/watch?v=yPf-RsseeEE
My youngest son just graduated last week with his mechanical engineering degree, he's going to Georgia Tech in the fall on a full scholarship to get his PhD. Out of the 50 engineering Master's degree graduates, 9 were from this country. All the rest of the were all from China or India. There were 11 PhD engineering graduates, 2 were from here, all the rest were from China or India. Not hard to understand why the US is losing technical jobs and leadership so quickly.
You seem to have a very limited viewpoint on what it takes to design something that works. Hopefully you'll prove me wrong and actually design and build something, but my impression so far of you is that of an "Internet Commando"!