I took a second stab at the gauss gun. This was intended to be a 3 stage version but I only cut brackets for 2 stages before the laser broke. There are 3 magnets to each bracket, with the middle one being large than the outer 2 to hold them in place. 2 sets of rails allow it to function at any angle and a small magnet holds the first ball bearing in a rest position ready for a shot (See the vertical pictures).
It's finished enough for me to learn what I needed to learn. The rails could be closer together, the magnet sandwich works well and ply seems to produce a slight bend to the rails if you're not careful. Now onto the 3rd version of the gun which will be a much bigger step up. (svg here)