Thulsa Doom and His Amazing Accuracy


Good ARs out of the box now, should be 2 MOA guns; that is capable of producing a group of a little over 2 inches measured from the center to center of the holes furthest away from each other, at 100 yards away. Materials that are easier to machine like 416, 410, 416l (not that some of those materials are particularly easy to machine) are more inclined to create tighter groups, as opposed to carbon alloy steels such as 4140, 4135, 4150, 4150cmv, etc. Conversely, chrome-lined barrels can be harder to group because of the addition of material into the barrel, and issues with uniformity of the addition. Chamber dimensions of course have a dramatic effect on accuracy as well, with the .223 Remington chamber being generally thought of as a more accurate (term used incorrectly) chambering than 5.56, and the .223 Wylde chambering splitting the difference between accuracy, and reliability during less than ideal conditions and out-of-spec ammunition. You can even get away with even tighter, more precise, and all together different chamber geometry's if you take the automatic component out of the rifle (like a single shot AR, or a bolt action).

At first glance, Thulsa has none of these things going for it in the accuracy department, but lets take a closer look! As for chamber dimensions, they may be a loose and reliable .556, but the tolerances of the Faxon barrel are so good, that you can simply create or purchase rounds of a geometry that take as much advantage of that chambering as possible; will it ever be a tight .223 chamber, no, but keep reading, I chart this up as a good thing! The barrel is hewn from 4150cmv alloy steel. It's probably the hardest commercial barrel material to machine but it also makes for the toughest barrels. Does accuracy suffer with this hard to machine steel? Probably! Faxon has kept incredible tolerances and immaculate finish work with this material however. chrome-lined bore? nope, this barrel is melonited, or carbo-nitrided. It is extremely hard, very corrosion resistant (better than many stainless steels) and leaves the initial geometry virtually unchanged, think Springfield XD, or Glock barrel)

Heavy Barrels are also thought of as more accurate. The truth is, heavy barrels do help soak heat that can cause a barrel to walk as it heats up. However, with modern barrel production techniques, properly relieved barrels don't really walk as much as they did twenty years ago. Now that is not to say that heavy barrels don't have a place. They can take more heat away from the chamber for a longer amount of time, increasing the life of machine gun barrels. They can increase accuracy shot to shot, by increased rigidity and again more mass to take heat. Thulsa has a Pencil profile barrel.

Bottom Line

I did apply a few tricks. Dropping and barrel in dry ice, heating the upper, and putting a .001 stainless shim in between the upper and barrel during assembly. Not over torquing the gas block. Using a free floated hand guard, using a to-the-limit of the spec bolt carrier, etc.

With 55gr. flat base, Berger bullets, I'm getting a little less than .75 MOA. No really. That's five shots from 100 yards away, using a USOMR-17 optic with loads from HSM (HS Munitions). I couldn't be happier. so, next time someone tells you you have to get a stainless barrel, or a .223 Wylde chamber, or a bare bore just to hang, we'll all know better. As for the profile of the barrel, I'm shooting these groups as fast as I can get them on target. This is a true .75MOA AR!

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