The barrels are button rifled and no build up called out, after a good cleaning the bore black is almost transparent. The barrels are on the market, have been since 2008 and they have always been faster than the other barrels on the market. Apples to apples? They are AR barrels being sold on the open market and they are faster.
The first 2 batches were chrome lined, after that Melonite treated. In 2008 Bison, Cardinal Armory and myself were the only ones making 6.8 barrels with 11 twist and the higher performance chamber that allowed us to load 110gr 6.8s 150-200fps faster than factory ammo.
When I got involved with the 6.8 I was determined to show everyone that the performance Holland, Murray and Lawton said was possible really was IF the barrels were made correctly. Other barrel makers were using 6 groove with apx a 40:60 land to groove ratio, some 50:50. I tested different twist rates, 4 groove, polygonal, 5R and 3 groove rifling along with different chamber designs during 2007 and 2008. In the end I settled on 11.25 twist 5R(my button design) with my chamber design. I can push 110gr bullets to 2800 fps out of those 16" barrels with off the shelf powder. No cratered or flattened primers, pressure around 58K.
For years I used Krieger, Bartlein, Broughton, Rock a few Douglas, Hart, Shilen, and Pac Nor but these are $200 button rifled AR barrels. I'm sure specs could be changed to increase velocity on the other barrels but so far they are slower, maybe it's not important to them.
ETA- As for the 5.56 barrels around 2010 I purchased 12 barrels from other makers and tested them, 11 were not impressive at all. 1 was more accurate and faster. I took all of them back to the shop and started inspecting, during that I found a .219 inspection pin would slide in the muzzle but stop apx 3/4" in on 11 of the barrels. I was pretty sure I knew why the pins stopped 3/4" in. The barrel that was tight (.218) all the way through was a 410 SS. I called Steve and said I have an idea about what's causing the problem, told him and he said I was correct and they had one extra step in their process to control that. I used that info on the barrels I produced, didn't really effect the 6.8 barrels with 5/8-24 thread.
