What is the difference between the Federal Lake City 5.56x45mm and the federal 855 green tip. New to all this and just trying to.learn

5.56x45 is the NATO designation; most commonly it's called "556" and is essentially the same as .223 Remington
M855 is the Military's model designation for a specific type of 5.56 NATO (weight & bullet design) it's still the same round.
http://en.wikipedia.org/w/index.php?title=5.56%C3%9745mm_NATO&redirect=no#M855A1

5.56 x 45 is the specification for a lack of better term for the .mil. .223 Rem is the SAAMI spec. Higher pressure in the 5.56 is the biggest difference. 5.56 is also usually crimped and sealed. .223 Rem is lower pressure and usually not sealed nor crimped.

There are many loads in 5.56 x 45: M193, M855, M855 A1, MK262, MK318, etc:
M193 is a 55gr FMJ bullet
M855 has a 62gr bullet with steel penetrator in the core. M855 A1 has a large exposed tip.
MK262 has a 77gr SMK OTM bullet
MK318 has a open tip, lead core with thick solid copper base.


Read the FAQ at the top of the forum.

The green tip has a steel core.  Penetrates hard targets better than lead core.