Bought new in early '89, attached to everything A2. It's a 20 inch heavy barrel, actually appears thicker under the handguards.

With the ejection port facing away from you, the barel is stamped in front(left) of the front sight post with SS then 5.56 underneath that, top and bottom rather than lengthwise. Under the handguards, at the base of the barrel is also stamped SS. Those are the only marking I find.

I can figure the "SS" is stainless steel. Who made it and how do I know the twist rate? Now for the dumb one - the barrel is black, I always thought SS was shiny?

Thanks for the help.

You definately got an olympic arms barrel. If it has the 5.56 SS markings this means that it is a button-rifled, 1X9 twist barrel. It is 416 stainless finished with black oxide, so don't play with it, you can't touch it up with bluing for obvious reasons. It is probably a .223 chamber as apposed to 5.56, being made before the mid nineties, don't worry, I pump hundreds of mil. 5.56 through it all day long, it doesn't matter in the real world. How do I know you ask? My carbine has the same markings. The finnish looked normal to me, so at first I thought "SS" denoted the new (at the time) SS109 round (my barrel was made before '86) But turns out to my surprise it was stainless after all. I type in "Ar15 barrel marked 5.56ss" on my search engine and it put me in the Olympic arms bbl. marking I.D. site. I forget the address, but try typing that in. It's also match grade, as they say all their bbls. are. My 16" is very accurate, so I can attest to that. Anyhow, good luck. Over and out.
_______________________________________________

62 grains, the little things that mean so much! [X]

Thanks for the great answer RABID. I took your search engine suggestion and ended up here:  http://www.olyarms.com/bblinfo.html and it just confirmed everything you had already told me.