Here we go. Both the toy space gnu and outfit are still works in progress, I had to rush everything a bit for this weekend. The gnu needs the M4 magwell adapter and VN straight shortie mag, more twiddly bits and a red torch shoved up the fake barrel, but if you want to make a chunky lasgun (and everything's chunky in the grimdark) then you really can just wrap a G36 in EVA foam (which is also what I've used for the armour).
The basic construction is 8 pieces:
#1: long contiguous side piece
#2: stock top (about 5cm wide, IIRC)
#3: vertical piece between stock and top
#4: top piece (about 6m wide, IIRC)
#5: front piece (shield shaped)
#6: magwell front
#7: magwell rear (a small piece just below the mag release)
#8 = #1 other side piece
Curve in both sides in front of the magwell to make a handguard, use some bits of PVC waste pipe as a fake barrel, whatever you've got to hand for the top tube and sights, bit of grip tape, twiddlies, and you're done. Impact adhesive or hot glue to hold it all together. The foam over the stock is heated and pressed in so that it's contoured around the hinge, which helps to keep everything nice and snug. There's no wobble in use and with some basic sights cut and dremmelled into the top posts it's accurate enough for CQB.
I've left it open up the back (the rear of the real stock is just visible) and all along underneath the stock and trigger up to the magwell (there's a small #7 cross piece at the back of the magwell at the bottom, underneath the release button). This means the G36 can just slide straight and out from the back. Cut some holes for the rear sling mount and the bumpy bit on the right hand side (still visible through a hole that I haven't yet covered) and they'll key into the foam and hold it nice and securely. The G36 is intact and unmodified apart from the rear sight being removed to help it fit, and the front rails just for lightness. I can get a small carabiner in to the sling mount through the hole in the left hand side.
The fire selectors are exposed on both sides, but you could probably cover one or both of them over as well.
The actual foam cutting and gluing only took an hour or so, the rest of the time is sanding, filler, sealer and paint.