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9/22/2017 12:11:25 AM
Posted: 9/17/2005 9:09:07 AM EDT
I'm hoping some one can help me ID this barrel.

The only markings are SUM 556 1:8.5

1:8.5 strikes me as a unique twist rate.

The barrel is .980" then steps down to .750 in the FSP area then steps down again to .720

Any ideas?

Link Posted: 9/17/2005 9:19:22 AM EDT
[Last Edit: 9/17/2005 9:21:36 AM EDT by Minuteman419]
Sounds like an Olympic Arms SUM Barrel to me.

ETA: Half way down this page.

Link Posted: 9/17/2005 9:23:17 AM EDT
Assuming it is, are they any good? I'm preparing for a new build and this one has been lying around for a while. The bore is in excellent shape and the last time I used it , I got good aqccuracy from 55 and 68 gr bullets. I assume 62 will work also.


Link Posted: 9/17/2005 9:27:39 AM EDT
Link Posted: 9/17/2005 9:33:44 AM EDT
Minuteman...you are the man!

It's definitely an Olympic Arms Stainless Ultra Match barrel.

These barrels are our most accurate barrels, and quite frankly, these are the most accurate AR-15 barrels on the market. These barrels have Broach-cut Rifling. What is that you say? Well, broaching is the method used to create the lands and grooves. For these barrels, we use the stamping "SUM" which means Stainless Ultra Match. SUM barrels are all chambered with minimum SAAMI 223 Remington reamers. These barrels can also be identified by looking down the bore. All of our broach-cut or Ultramatch barrels have only 4 lands and 4 grooves.

I just verified it has 4 lands and grooves. Now the 64K question, is it any good?

Many thanks!

Link Posted: 9/17/2005 10:30:02 AM EDT
I've read in several threads on here over time that these barrels are very accurate.

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