The Firing Line Forums

Go Back   The Firing Line Forums > The Hide > The Art of the Rifle: Semi-automatics

Thread Tools Search this Thread
Old October 9, 2012, 01:05 PM   #1
Join Date: December 2, 2007
Location: Sugar Land, Texas
Posts: 57
Help me Identify an AR Upper!

I've been working on a budget AR build after winning a complete Frontier polymer lower for $75. After placing a WTT/WTB add for a complete upper locally, I met with an LEO who traded me an older upper he had for my Kahr PM9. I valued my Kahr at around $525 (even though I only paid $325 for it), was wondering how y'all thought I did.

It's a 20" upper with bcg. Looks used but in good shape. Has forward assist and dust cover. He said it was an Olympic arms upper but nowhere is it stamped with the manufacturer. It doesn't have a railed gas block which I find odd for a factory upper, it will be scoped anyway. The only markings are on the barrel where it says:

SUM 5.56
Can anyone confirm this as an Olympic arms? And how did I do on the trade?

for ID:
darestie is offline  
Old October 9, 2012, 04:48 PM   #2
Senior Member
Join Date: February 8, 2008
Location: Denver, CO
Posts: 1,925
Upper receivers aren't marked, with a few exceptions like PSA.

Do you see anything on the barrel indicating if it's 1/7 twist or 1/9?

An upper like that can usually go for anywhere from $400-$550 new, depending on a couple things.
Ridge_Runner_5 is offline  
Old October 9, 2012, 05:24 PM   #3
Senior Member
Join Date: May 29, 2007
Location: St. Louis, MO area
Posts: 4,039
The first result on an internet search for "SUM 5.56 barrel marking" comes up with an Olympic Arms website. That page says "SUM" stands for "stainless ultra match," supposedly Oly's most accurate barrel. HOWEVER, they also say they only chamber those in .223, not 5.56, so that is a discrepancy. That same page does say that they use a black oxide finish on their stainless barrels, and that requires a bit more care than the usual parkerizing on a normal carbon steel barrel.

In regards to the chambering, this page appears to be an Olympic Arms owners' forum, and indicates that even though the barrel is stamped 5.56, it has a .223 chamber (as per Olympic's site, that would be a SAAMI minimum spec .223 chamber- a VERY tight one).

Therefore, yes, it looks like an Olympic upper (or at least barrel, which is the important part). Moreover, it's a minimum spec .223 chamber, so I'd caution you against using any 5.56x45 ammunition in it. The throat in a .223 chamber is slightly tighter and the pressure spec slightly lower; using 5.56 in the rifle might well be fine, but you're risking a dangerous situation. On the bright side, Olympic Arms has a rep for accuracy, so I'd anticipate if you feed it quality .223 ammo it should be a real tack driver.
Technosavant is offline  
Old October 9, 2012, 05:33 PM   #4
Senior Member
Join Date: May 28, 2005
Location: Texas
Posts: 6,231
That forearm looks like the one on my old Olympic Arms. I had an upper with one just like that. They have a railed one that fits and it only cost me about $100.00. Mine fit on the same barrel nut as the smooth forearm.

It is $167 now but still not too bad.
Have a nice day at the range

NRA Life Member
Eghad is offline  

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT -5. The time now is 07:44 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2017 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent:
Contact Us
Page generated in 0.05594 seconds with 9 queries