Quoted:
very interesting to see a hollow cavity in the nose of the bullet. I'd like to see some bullets after contact and gelatin test.
OTM = open tip match. that black area is lead.
this open tip is the result of drawing the copper jacket from the base upwards over the lead, rather than the typical other way around. it has virtually no effect on performance in tissue –– the primary wounding mechanism with OTM is the same as traditional ball, namely fragmentation. one primary advantage of OTM is that the base is more uniform, and there is less initial upset of the bullet as it leaves the muzzle. this improves accuracy considerably.
the 77gr Mk262 construction is the same.
http://en.wikipedia.org/wiki/5.56x45mm_NATO#Mk_262
ETA: OTM is *not* classified as a "hollow point". JAG ruled several years ago that OTM ammo was *not* in violation of the Hague Conventions, and can therefore be lawfully employed by the US military.
ar-jedi