The grenade launcher is just the muzzle brake looking thing on the end of the barrel, along with a flip up grenade sight. I'll post pictures of it tomorow.

As for grenades- you can't buy them, or if you could, you would have to pay the $200 destructive device tax for each one- very costly fun. Fortunately, you can make dummy grenades very easily. You need a few M1A2 grenade adaptors (see http://samcoglobal.com/access.html) and you attach a tennis ball to the adaptor and hold it in place with electrical tape. All you need is 7.62x39 blanks to launch them up to about 200 yards.