Looks like that would be right, IF you removed the ejection port door, pin & spring.
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It would seem that if you purchased this unit bare/stripped it would meet advertising claims. Does it ship with the ejection port?
Its seems its heavier to a comprable standard style unit with no forward assist. But isn't it a stiffer/stronger unit? There is always a trade off between weight and strength so its seem to me that its a heavier stiffer unit at the expense of weight. There is always a tradeoff between weight, strength and expense.
Email Vltor, or call them and ask about it. I don't see this is a massive conspiracy, but if it bugs you contact them and get an answer.
Look at the rail companies that give a weight without the barrel nut, its the same sort of thing that gets people confused. Its not inaccurate, but it can be hard for people to figure out at a quick glance.
I just received a brand new MUR-1S and the weight is 8.2 oz or 234 grams. Slightly off topic, the receiver extension fit and slightly loose compared to the snug/tight fight of my MUR-1A. It rocks a little without the barrel nut.
http://i103.photobucket.com/albums/m...n/IMG_4313.jpg