I really like the BRG-15, it's a pity FN were in a bit of financial bother at the time they were trying to sell it (to save money, they shelved it in favour of making the less expensive but potentially higher selling, P90).
Essentially a European heavy machinegun to outperform the Soviet KPV, it had both left and right feeds (to give it dual feed ability) and ejected cases out the bottom. As expected, the rounds were massive.
There doesn't seem to be a lot of info about it on the net and even my copies of Jane's Infantry Weapons don't have much more to add except this one bit -- it also had selective fire capability.
Aside from the following general info webpages, the last link I've listed is worth a read (and a good look at the images) because it shows the BRG-15 round side by side with a .50 BMG round.
https://translate.google.com.au/tran...-text=&act=url Google Translate version of Ukrainian language page (has more technical info than any other page I've seen). Some words are not translated because they are combinations of two or more root words but note that the root word "brone" generally refers to armour/armoured.
http://world.guns.ru/machine/be/fn-brg-15-e.html general info
http://www.cartrology.com/browse-amm...ry&exhibitID=3 basic cartridge comparison picture
http://www.warrelics.eu/forum/ordnan...g-15-a-180356/ pictures of .50BMG next to the 15.5x106mm BRG-15 round