Just picked this 20rd bag up at my local gun store....Can anyone tell what type of bullet this is......It has a green tip on it but not sure if that has anything to do with it......They seem to be reloads.....

The XM855 are the military SS109 M855 penetrator rounds.  Basically it is a copper jacket over a tungsten steel core.  They will penetrate up to 1/4" of steel plating with no issue.

The XM designates that they are military seconds, just like the XM193 is not M193.  Basically Federal gets five gallon drums full of rejected military ammo, sorts them, inspects them, and repackages into cases of 20 round boxes, and loose packed 1000 round boxes.  Looks like the store you bought them from got the 1000 round loose pack and then put them in a plastic bag to sell them in smaller quantities.

The XM stuff is OK, but not the best defense ammo as it is not first quality.  It is great for target practice on outdoor ranges, but not indoor.

It is a mild steel insert, not a tungsten core.  The M995 armor piercing round uses a tungsten carbide core.