sorry bout that I was ust wondering about how to make it way stronger...
No need to be sorry man, I was just being blunt and telling it how it was.
So you would like it strong....that is why I strongly recommended against using drywall on the first page of this thread, as drywall is not strong. Read through Sandbagger's posts in this thread, and you will see he suggested using cardboard and wood glue, and alternating the direction of the corrugation in the cardboard. This is similar to how plywood is made (alternating grain directions) and should add a decent amount of strength. You seem to have your heart set on using fiberglass, so along those lines, I'd recommend adding one or two very lights coats of resin to the outside of the prop to harden and seal it. But don't do this if you use any foams for details. It doesn't harm eva foam, but still retains a rather soft texture and doesn't look all that great (speaking from experience).
Now why does it have to be so strong? My weapons are eva foam with pretty minimal reinforcement, and hold up very well at conventions, look awesome (it's tough being modest), and are light enough to be comfortable carrying around for hours. Certain parts wouldn't hold up super well if they were sat on or thrown around, but they are more than strong enough for my needs.
Also, it's definitely worth it to fork out a little bit of money for good materials. I know we disputed on contact cement a little while back when you told someone that it wasn't good for foam, despite it being one of the best adhesives for foam detailing. You then mentioned that you got yours from the dollar store. Don't get me wrong, I get lots of little items from the dollar store for my cosplay work, but for adhesives, tools, and such, it's worth it to by decent consumer grade products from a large chain store like home depot, Lowes, wal mart, etc. Also don't be afraid to ask other members what brands and products they've had good luck with, that's kinda why we are all here helping each other out!
Now let's see this rail gun get built man! I haven't seen many, and it will be great to follow your progress!