I know what you mean, October. I finished the costume some time ago. There are pictures in my gallery (including my avatar). It wasn't all that expensive. I bought a broken M4 from Kapowwe. They have a section on their site with stuff that's already broken, and since you essentially have to break the gun as it is to make the Patriot, it doesn't matter whether it's already broken. I think I got it for $10 in 2010.
It's a hundred-round magazine, but it's homemade because the real thing would be very expensive for an airsoft gun and was impossible to find to fit an M-4.
Can the magazine be used on any other assault rifle?