The reason I suggested carbon is because you can buy very thin carbon tubes from TAP Plastics. And I believe they're pretty cheap. The thought was that you'd cover the brass rails with them for firing and discard them after they're ablated too much. Just a thought. I'm cool with you not sharing pic. I'm most definitely not a fed (though I guess that's just what a fed would say). I'm just a dude who's dabbled in other projectile type projects and love this stuff.