Does anyone know if the prototype 25 round AR15 magazines were made out of steel (like waffle magazines), or aluminum (like standard 20 round magazines)?  I want to have a few fabricated, and don't know which route, material wise, to go.  I know what someone will say:  "you held two of the prototype rifles a few weeks ago - you tell US".  To be honest, I was so excited about holding the weapons that I failed to notice MANY things.  Also, does anyone know if the prototype gas tubes were made of stainless steel, or polished aluminum?  THAT, I did notice, but I don't know which material was used.  My best guess is polished aluminum, so I'm taking an unmodified early gas tube and polishing off the parkerizing to use on my build.

Prototype mags were made with aluminum bodies, followers, and floorplates.

And gas tubes should have been carbon steel, not stainless and certainly not aluminum.  I don't think an aluminum gas tube would fare too well after a few mag dumps.

My mistake.  I did not mean gas tube.  I meant to say "buffer tube".  The buffer tubes on the prototypes appeared to be either polished aluminum or stainless steel, instead of the anodized aluminum that was used later.