There's no question about which is more intimidating. The 8mm BB has a reputation at least to greater psychological impact than the standard 6mm BB. Having been at the receiving end of incoming 8mm fire I can tell you that nothing puts your head down faster than a stream of 8mm plastic coming at you. From the awed looks that you get while holding a packet of eights in the loading area, to the gaping void that is the unusually large barrel. The caliber of the 8mm is larger than the caliber of many a real firearm. However it is often argued that they hurt equal or less than their 6mm counterparts due to a larger surface area of impact.
In this Bite The Bullet article we have a special video presentation brought to you by the dedicated professionals at the Redwolf Labs. We will stop at no obstacle to destroy or confirm the myth that 8mm BBs hurt less than 6mm BBs.
Bite the Bullet 
