McMillan Group International has a well-deserved reputation in the firearms industry. Take a moment to watch this short video they just posted on Facebook. It's their "HELRASR" in .50 BMG.
"We had an awesome day at the range yesterday. We have been working on this project for years and seem to be getting near the end. Take a look and let us know what you think." from the McMillan Group International Facebook page.
McMillan Group International: http://www.mcmillanusa.com/
I'll bring you more info if and when I get it. In the meantime, monitor their social media (which you ought to be doing anyway).