Those are FMJ. M193 is 55 grain lead core. M855 (was SS109) is 62 grain penetrator core.

If you are talking about Federal the X prefix denotes seconds. They aren't but it's a way they are able to sell mil ammo to civilians. The F, BK, and other suffix denotes the packaging. Bulk, boxes, stripper clips etc.

 

Look no futher for the answers you seek.

http://www.ar15.com/ammo/

 

Are they all FMJ or does "MILSPEC" hollow-point exist?

With VERY limited exceptions our military does it use hollow points due to the Hague Convention of 1899. Thus, you aren't going to find MILSPEC hollow points.

 

Tell the USMC that.

http://bulletin.accurateshooter.com/2010/02/usmc-adopts-new-open-tip-sost-5-56-ammo/

I don't have the time right now to dig but the DoD cleared the use of OTM ammo for snipers sometime around the first Gulf War. The USMC Mk318 Mod 0 ammo is similary termed open tip IIRC but it is called "Ball" in it's formal military nomeclature. Obstensibly it is barrier blind and the open tip helps the bullet's flight, but it acts like a hollow point in flesh.

There are numerous exception to HPs/JHPs being banned for military use.

http://kitup.military.com/2011/03/warfare-is-deadly-bullets-oughta-be-too.html

As a sidenote....M118 ammo was the ball ammo used by snipers. M-852 .308. was OTM(SMK) ammo for competition. The open tip M-852 was meant for match use only. On the sides of the ammo cans it came in it said "NOT FOR COMBAT USE." I have two cans of it. But the M-852 was approved for combat use in the early 90's.