Two questions about these rifles
 

I have a couple of questions:

http://www.imfdb.org/images/1/1b/SIG550.jpg

Is that a 20 round magazine? It looks too small to be a 30 rounder to me, but I'm no expert and I'd like to be sure because I'm making a mod for S.T.A.L.K.E.R. that changes how the weapons behave, and the SIG SG-550 model in it has a magazine of that size, but holds 30 rounds. I want to be sure that's wrong before I change it.

http://www.imfdb.org/images/b/b8/ColtM177E2.jpg

What is that on the end of the barrel? Is it a muzzle brake?

On the Colt XM177E2 that's a flashhider and slight sound suppressor. In Vietnam, those short barrels, created a huge muzzle flash and loud rifle reports. They were called moderators. Any of the them seen in films are fakes.

You can see this note on the M16 page.

"Movie Armorer's note: Since the ATF viewed the flashhider of the XM177 as a 'silencer' due to the sound baffles within the item, it was as strictly controlled as any other silencer. Also the interior design of the flash hider / sound suppressor of the XM177 made it difficult to adapt to fire movie blanks. Thus there are virtually NO real XM177s used in movies. Most of the versions seen in films are modified commercial SP1 Carbines/M16 shorties with 'fake' XM177 flash hiders slipped over or welded to the end of the barrel. Also movie armorers used aftermarket barreled uppers by third party manufacturers and mated them to existing fully automatic lower receivers, thus were constantly swapping parts to build up guns which were requested by movie directors. So it is possible to see various upper receiver assemblies on recognizable M16/A1/A2 lower receivers.''

Flash hiders usually have 5 or 6 long slots. While muzzle brakes have a bunch of port holes.

That's a 20 round magazine. Here's a 30.

http://upload.wikimedia.org/wikipedi...gw_90_kurz.jpg

Thank you! :)