Well, right now the XL70 is quite great example of PLASTICOOL BULLSHIT - worthless right now. Should be balanced abit.Actually 5mm aint 5.56mm. 5.56mm(x45mm if im right) is .223 caliber and the minigun/assault rifle 5mm is fictional ammo.
Actually 5.56x45 is slightly modified .223. .223 weapon cannot use 5.56, but 5.56 weapon can use .223..223= civilian round5.56= military round (more gunpowder)
Did some little research on this and yeah, youre right - they have the same dimensions except the shape is a little different. While thinking about this, i tought that technically (and of course logically) the ammo M60 and FN FAL is using (7.62x?(was it 51?)) is stronger because of its size and powder ammount than the .223 (wich actually is a sporting round) while in-game .233 is times more worth and better. But alright, thats another story.