@HandyDave Me too brother. 
I had seen BMG 50 door guns in B-17’s and B-24’s before, but some 28 years ago now I saw my first BMG 50 cal. rifle.
One evening, a buddy of mine at the time (a very tall hippie guy about 10 yrs older than me) stopped by the house. He said he was heading up the road to visit one of his lifelong friends who lived in another little town about 12 miles north of us, and he had been given permission to bring me along. He wouldn’t tell me why, but he said I would enjoy the visit. (He obviously had something specific in mind that he knew I would like)
Now I didn’t know, nor had I ever met his friend, and although I wouldn’t exactly call him an anarchist (for lack of a better description), I did know one thing. He was the kind of man you didn’t just show up at his home having someone else with you and those who were invited and welcome in his home (which were very, very few) had earned his trust and respect in order to have that privilege.
The only other way was if in “Extremely Rare” instances, such as mine, you were invited and welcome on the word alone of someone belonging to an even smaller “inner circle of trusted”, and the number of people whose word alone was good enough was so small as to be all but non-existent.
So off we went.
We arrived at his home and after introductions, we proceeded to have a cocktail or two or three (four?), enjoyed some good conversation and got to know each other a little better.
After a spell the gentlemen looked at my buddy (whose last name was Pike) with a little grin, then back at me and said,
“The Commander”… (As in “Commander Pike” from the original Star Trek. It took nearly four years for me to learn the meaning behind the nickname “Commander” LOL)…mentioned I have something you would probably enjoy having a look at.
He got up, went out of the room for a moment, came back with a large black hard case, set it down on the floor in front of me and said, “tell me what you think”.
I could have, in a million years, never guessed what I was about to see…
I opened the case, and there before me was a Barret 50, one ported??? barrel, two scalloped barrels, a bi-pod, and a scope that to this day I have no idea what was, other than magnificent.
I was, (and this, as a rule, is pretty uncommon for me), absolutely SPEECHLESS!!!
WOW…What a magnificent piece of hardware!