it looks great! finally another person that takes a decent amount of time in unfolding something in pepakura. you can really tell when someone takes their time unfolding something correctly. and I'm impressed. ill definitely build this soon.
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edit-
just from eyeballing it, it seems to be pretty close to proper scale. weapons are hard due to the face pepakura can only plot the assembled height. so you have to do a little measuring to plot the overall length.
one thing that helps is to change the axis on the weapon, so that it stands vertically on its tip, then the assembled height magically becomes the length and you can build it to whatever size you please, if you build it to the official specs, its going to be a very big gun and look funny to hold, (its supposed to be held by a 7ft spartan) so scale it according to you, not master chief..