@padom always comes up with something unique.
Lots of opinions on this thread. I probably cannot add much value beyond what has been written, so I will be brief. Base upon the facts given, I would advocate for a factory Criterion barrel. Steve and Stephanie D. continue to innovate. As much as CLE is my go-to smith for great barrels, if you are shooting M193, I would not spend extra for Frank's expertise. That is not a put-down to Criterion, either.
Also, I have add props to BAT for extensions, since JP was mentioned.
Well, John Scandale (Keystone Accuracy) isn't really that unique, if that's what you mean. John just isn't a major advertiser, and caters mostly to competitors.
He's a pretty damned good shooter as well. Shot for the All Guard Highpower teams, won the 1,000 Yard Service Rifle National Championship, Distinguished High Master...that kinda thing. He is an experienced machinist, uses quality inputs, and a high-precision CNC; the result is a high-quality output. His stock blank is a Green Mountain, and he keeps Krieger on the shelf as well.
A note about Keystone Accuracy: his rimfire trainers are
special. Functioning up-to-and-including full-auto, they are still capable of 1 MOA or better, with good ammo. At 100 yards--a litmus for .22 rifles--they will clean standard targets that were intended more for Anschutz, et al. bolt guns.
Of the smiths and shops out there, there are only TWO that I prefer to work with, and THREE whose shops I would feel comfortable with if I needed a really accurate AR-15. In my order of preference, those are:
1) John Holliger and staff at
White Oak Armament. Best AR barrel I ever had came out of this shop. My 600 yard 80 SMK loads grouped in the 4's with A2 Irons.
2) John Scandale at
Keystone Accuracy. My 1,000 yard upper was put together by Keystone, along with probably the most accurate rimfire Trainer in the entire midwest...it would beat the dogshit out of your factory Sav-CZ-uger, and for a blow-back AR upper with a conversion kit, that's really something.
3) Frank White and staff at
Compass Lake Engineering. Frank and I had some nasty words once, but I will say, if you need anything really custom, or a special part made, Frank's the guy. CLE is MAKING a lot of the parts and tools some other shops sell and use. Just be careful with his chamber...it's short, and tight.
Derrick Martin (Accuracy Speaks) and Bill Wylde would have been on my list at one time, but they're not doing much work anymore. Maybe Scott Medesha, but same.
As with many other things, as far as accuracy with an AR, it really depends on how fast you need that rifle to go. I have been down the road a long, long way. They can do amazing things if you need them to badly enough.
-Nate