My gfs dad has a sig AR that is very different from the standard ARs. It does not have a charging handle but has a bolt slide on the side of the rifle. It does look pretty cool and is fun to shoot but is very heavy. IS it truly an AR? I just don't think it would be much fun because its not compatable with the wide variety of parts and upgrades we can do with a standard AR. I expect they would be more complicated to build and harder to clean as well. What's with these?