I am trying to do research. I have only tried to mention what I have seen, or have failed to see. It has been several years since the only time I have shot any of Marks guns (I managed to get to a range day). At that time, I don't think the tOBR or OBR Lite had been introduced - so I think I shot Stealth 5.56 and 7.62 Predator and OBR (and the only thing I was really aware of is one 7.62 was lighter than the other (I did not know what to look for).
Anyway, I am trying to compare these guns mostly off of look at tiny pictures on my computer screen - which may or may not have been choose to illustrate differences. From those little pictures, it looks like Mark is using a fairly common lower between his production lines (The 7.62 OBR having a different stock). I think it has been mentioned that he is now using a common trigger (MBT). I can see the difference in the top rail easier on the 7.62 pictures than the 5.56 pictures (many of the pictures have covers/panels on the hand guard, which make it harder to see what is underneath).
I highly suspect there are many places on his rifles that I am unaware of that can be different, but I trust Mark to have made differences to focus on the purpose of the rifle, rather than market segmentation.
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Finally I have only built a couple ar's and torn down 1 factory build. So I don't know what is normal for the industry. Much of my assumptions come from the one LaRue part I own - a bolt carrier group. When I see Mark staked his gas keys, and another manufacturer did not bother - it make be believe Mark is focusing on details. I don't know if his gas blocks are pinned, if his castle nuts are peened, or any one of other details I don't know enough to even look for. I simply assume that that focus on details is present in all his products, because I saw it on one part. (Much in the same way another brand (that I will not name), has made me question their attention to detail simply because of one budget part.
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Anyway, I am sorry if I offended anyone on this sub-forum. Time for me to go back home to GD.