In the U.S. of A. the .50BMG ammo is readily available at about +/- $2.00 per round ($1.00 for reloads).
.50 Cal Firearms are legal in most every state (save but a handful), even though they have not been linked to crime, & for no valid reasons, some Nanny States have made them
'temporarily' illegal. The NRA is pressing the fight to reverse that.
In the end if you live in the U.S. of A., & can afford the hefty price tag for say the
Barrett Model 82A1 (as low as $7,800, but up to $9,200 US), & don't mind spending about $2 a round for the sheer fun of firing it, it's there just for the asking.................where you need not have any
"NEED", & need not prove any.
Barrett 2015 Product BrochureBTW.....hope you know someone that has a 2000+ yard backyard to play in, because it looks like to enjoy this toy you'll need a lotta room ta ramble in.
Where else but In the Land of the Free, & the Home of the Brave!!!

Looks like a fun way to spend a lazy afternoon with the boys ,,,,,,,,,,,,,,,,,, & without the need for any beers.

Disarming the USA??? ...... Yeahhhh, Riiiiiight!!