try using a dremel tool if you have one, works real well with an abrasive disk.

I've made oxy/acetalyne guns before for the movie industry with great success. I whole project involves a lot of testing for no two guns use the same fuel ratio, even if they are built identically. You can shoot some types of ammo with good success as well, tennis balls and bowling balls work great....

Very cool gun. I'm looking to build a metal gun myself. Great stuff to look at for ideas.

WOW, very cool. Keep up the great work and can't wait to see what you come with next.

One of the coolest guns I've seen. Very clean look.

Great first gun and great pics. Love the soda can damage. Keep up the good work.

Be sure to use the primer, it makes a world of difference.

This sounds way cool. Love to see more pics. Might have to try one of my own.