I've been shopping for 5.56 ammo.  It seems like the most common cartridge types I see are M193 and M855. Sometimes I see an "X" in front of the M and or and "I" or "J" at the end.  What do these letters mean?  If I'm buying for an indoor range, is there any advantage to M193 or M855?  Thanks.  If these are stupid questions, feel free to let me have it.

indoor ranges don't allow the green tipped ammo or tracer rounds, thats about as much as I know

I believe that Clinton stopped the sale of true military surplus, but if for some reason the rounds are not up to spec (and these are often cosmetic reasons), they designate that with an "X" in front of the military nomenclature for that round. Essentially, XM855 or XM193 are seconds that are allowed to be sold off.

 

That's my story and I'm sticking to it. Actually, that is what I have heard - can't vouch for the info so someone more knowledgeable may have to give you the straight story.

 

Green tip ammo (855) does have a steel penetrator, but it is not classified as "armor piercing", but as OG said, some ranges, with metal backstops, may not allow its use.

 

Adios,

 

Pizza Bob

^^ thats the way I understand it.

Bob is 100% on the money.  If it is listed with the X it is almost always Lake City ammo regardless of whos name is on the box (usually american eagle or federal).  Some smaller ammo manufacturers will just call it m193 or m855 and it is just a clone of the LC ammo.  Not all of it is bad though I think PMC drops the X and their ammo isnt half bad.  Another confusion piont is I have seen people list XM855 as SS109, again, largely the same product.

The last letter (A, J, etc..) is a packaging identifier.  I cannot find my decoding info to tell you exactly what it means.  The packaginf options are:  loose, boxed 20rds, stripper clips,  and boxed stripper clip 30 rnds. 

Ken

Another confusion piont is I have seen people list XM855 as SS109,

IIRC, SS109 refers to the bullet only - the 62 gr green tip with steel penetrator. M855 designates the entire cartridge - which is loaded with SS109 bullets.

IIRC, SS109 refers to the bullet only - the 62 gr green tip with steel penetrator. M855 designates the entire cartridge - which is loaded with SS109 bullets.

That is correct.  I have seen m855 listed simply as ss109 a couple of times now.  It is an incorrect use of numbers for sure!

Ken

Clinton did indeed stop the sale of US military surplus.

 

What military is Lake City making M193 for? None. Not sure how XM193 failed spec.

 

SS109 is indeed the head, and complete cartridges have been called that, rightly or wrongly, since the 1980s when it was born. M855 is an American designation, not a NATO designation. For all I know, there are countries that call their service ammo SS109. I know the Port I bought in the 80s was marked that way on the box and it was NATO ammo.

 

The "penetrator" in SS109 is interesting. Yes, it's certainly not AP. It has a flat tip. Never seen an AP component with a flat tip. Yes, the fact that is steel can increase penetration a little. Even though it has a flat tip. But it's not in there for that reason, they would have pointed it. It's in there to control the spin and yaw at 500 meters for penetration of thin steel at the specified range. It's in there to move the mass moment of inertia rearward in a Spitzer-type projectile.

edit: answered.

From the Army TM on 5.56 cartridges................

TM43-0001-27.pdf