Thulsa AR-15

So How Much does it Weigh?

It's so light that I can easily shoot it with one hand like a pistol; amazingly light. It's weird to hold it's so light. Thulsa comes in at 5.4 pounds. To put that into perspective, Robar's PolymAR is touted as 5 pounds with a polymer upper and lower. The Purpose built VSeven AR featured in an AR magazine was 5Lbs. 1.6 ounces. That's pretty close to my 5 Lbs. 6.4 ounces except with a full weight carrier, buffer, rifle length stock and spring, and a mid-length gas system. I'm happy.

My take on an ultra-lite AR

Anything I design/engineer/build I put through my triangle of quality; that being, materials - tolerances - engineering. It seems like a lot of people today are either trying to turn an AR into a pistol, and if not a pistol, then they are trying to turn it into an AK. The fact is (in my opinion), a pistol AR is just about as bad a firearm as can be built. The system was not designed to cycle effectively at those barrel lengths, the sights are a good 4 inches off target at any pistol distances, and the round is Horribly underpowered to be called a rifle round. In fact, all one has to do is go to to understand that for the length of barrel a magnum handgun, or even a .45 Super would have been a better choice. The old adage of "use a pistol to fight your way back to the rifle you should have had" simply does not apply to running back to grab a pistol AR. A 10mm Glock or a magazine full of .45 Super in a long barreled XD would be a better, more reliable, more powerful, more accurate (simply for sight offset's sake), and more compact (getting around corners) option. OK so what about turning your Direct Impingment AR into a piston powerhouse? Well what are you doing with it? The AR at it's very core was designed to be LIGHT, fast, and accurate. Instead of modifying an AR to be an AK, why not just modify an AK to keep the bolt back on the last round (they ARE out there, yes, even when the magazine is removed). While it is a testament to the AR's modular design that it can be adapted to fit a random requirement so readily (perhaps the most adaptable rifle in the world), it is going against the soul of the AR design to adapt the rifle in this way. The PVAR, the HK 416, LWRC, etc. make a fine piston rifle; the PVAR will actually fire multiple rounds fully submerged underwater! These examples are all fine guns, but the beauty of an AR and part of the genius of the design is it's weight. ARs are reliable, regardless of what you hear. A greased carrier and bolt will go for 1000 plus rounds in modern ARs, even carbine length gas systems. So for a light-weight rifle powered carbine, I started with an AR pattern, obvious really (of course there is so much info out there now you don't have to be an expert to build one either, and I'm not.)

The original designs had titanium flash hiders, composite, etc... Light! Following this logic I built Thulsa DOOM, the name of Conan's nemesis in the movies. Thulsa was a homogenization of Howard's bad guys from the books, of course. The name comes not from the antagonist's "evilness", but of his answer to "The riddle of steel". "What is a sword but the hand that wields it?" You can find more of Robert Howard's work here FREE: Adventures of Conan

Light as possible, but not the lightest

People are cutting mag-wells, grips, lightning carriers, buffers etc. I will never cut a grip or a mag-well, or do any strength compromising cuts. This is a tool (in my opinion) and it is serious business to me. If I had a billion dollars, I'd have a lot of ARs, most of them toys. I simply cannot afford to make an AR I cannot trust. Thus Thulsa has a full length (Magpul) grip, it's just what I had, and no cuts anywhere on the lower receiver. It is a standard FORGED lower of 7075 AL. If I could do it over, I would get V Seven Weapon Systems' Lithium-Aluminum alloy upper and lower.

I started with a Titanium (VSeven) birdcage AR flash hider for weight, but I ended up putting my precision Armament brake on it, it's just too good. If I had to do it over, there are some TI brake options coming out now. I don't know what erosion will be like with those, but the A2 birdcage didn't show any signs of erosion in the few thousand rounds that were shot through it.

The barrel is a 16 inch, pencil profile, melonited, mid-length gas system, barrel by Faxon. I couldn't be happier. I had sort of used the M4 as a baseline for this build and made it the gun to beat. This is a 1 MOA barrel with the right ammo, and when it gets hot it's a 4 MOA barrel. The M4 is a 4 MOA gun out of the box cold, so score for Thulsa. The thin barrel does get hot fast but I can slam through 5 30 round mags as fast as I can pull the trigger without any hiccups (might do better, I just haven't tested). The lighter barrel may have less propensity to droop than the heavier M4 at it's failure point, I don't know. I could have gone to a 14.5 inch barrel and pinned on a muzzle brake to get me to the tax defying 16 inches, but I went with the 16 incher for a couple of reasons... One is, it's already lighter than the M4, with more power! However, the real reason is that I can get the mid-length gas system. It is heavier, as it must now use a longer gas tube, and thus a longer hand-guard to protect it (and your hand). The benefits though are there; slower more reliable cycling, perhaps a cleaner action, better part life, and a more pleasing bump on the arm. I'm not sure if this aids in accuracy or not, but this is a 1 MOA gun with 69 Gr. Black-hills Sierras. It is 4150 Melonited steel. There was a recent article about how bad meloniting AR parts is. It was a single manufacturer saying this, and I believe they were trying to sell their cheaper components. They went on to say that MIM parts (like the bolt catch) were better.. I'm not a gun manufacturer, so I REALLY DON'T KNOW, but I smell bullshit. As far as my experience goes with carbo-nitriding though, it's great. I've got a .45 with 70,000 plus rounds through it, that's even been in the ocean, that has no rust, and is still quite accurate. Modern pistols and AR internals (aside from barrels) do not "wear" through, they break. I was after it because it is a more accurate option than chrome for bore protection and it is very corrosion resistant on the outside. So far I couldn't be more pleased. After many thousands of rounds, there is no head-space change as was promised to me from that same bunk article, and nothing has cracked or smushed, etc. The noticeable plus aside from an un-oiled, corrosion free gun, is that cleaning the bore (if you're into that) is FAST. I mean easy, fowling comes off fast. I'm hoping that the barrel life will be increased as well. Alexander arms I believe recommended in some article I was reading to locktite a barrel in place for increased accuracy. I just used moly-grease ON EVERYTHING; this is the way it is recommended in the mil manuals. When torquing using a barrel nut tool, put your torque wrench at 90 degrees to the crows-foot/tool otherwise you will have to account for the added length of leverage of the tool being used.

The gas tube is made from inconal. This may be a mistake as manufacturers typically engineer the gas tube to fail before the barrel does, as a safety. I popped it on for it's corrosion resistance, as it's pretty much the same weight as anything else I would have put in there. A good install note however: run a copper coat hanger through the gas tube before you install it. There was a "coin" of steel still attached to where they drilled the port hole in the tube. This would no doubt on the first firing, have dislodged and jammed into the gaskey port, where I would have to disassemble (buy new gaskey bolts every time) the carrier, to fix the instant short cycling it would have caused.

For the gas block, I went with a titanium, pinned, low profile (light, and gives me the ability to use smaller diameter hand-guards) gas-block from V Seven. There are aluminum gas-blocks out there, but the heat erosion and the thermal expansion coefficient delta for aluminum vs. steel makes it a stupid choice for a gas block. Ti is lighter than steel, and has a higher strength to weight ratio. Plus under heat Ti expands LESS than steel = tighter seal??? Maybe, I don't know, but it works great, it stays tight hot or cold, no pins/screws have walked, and I love it. I did peen the screws in place. (no loctite, it gets hot up there)

I went with the lancer systems carbon-fiber hand-guard. There are lighter options, and if I had to do it again I would probably go back to V Seven and get their 2099 Lithium Alloy Aluminum hand-guard... I love those guys. I went carbon because it's light, but also because it takes heat fast, and I want that barrel cool. The gun does get hot fast, but it also cools fast. After a long rifle stage at a three-gun with many rounds spent, my gun will get hot, but it will be the first to cool, and it's never been too hot to hold. (not that you can't get it that way if you tried) I specifically went with the Lancer Systems hand-guard because you can properly torque their barrel nut, then align the hand-guard separately. There are a lot of systems out there, especially in carbon fiber, that will blow your torque specs out of the water when it comes time to align the hand-guard. Does this matter? I don't know, but I've got a really straight shooting gun. I also replaced the stock steel screws with Titanium ones, and loctited. It doesn't make really any weight difference, but I had them and I like the look.

The upper receiver is from V Seven, it is forged 7075 and doesn't even have previsions for a forward assist or a dust cover. LIGHT! ARs don't need dust covers; go ahead and hate-mail me. They are not open bolt guns. There, I said it. I wouldn't have installed a dust cover on this build anyway to save weight, so the bosses to install one would have been superfluous anyway. Now lets talk about that forward assist. If your rifle isn't chambering on it's own, fix it before you start shooting. If you're in a fight, tap, rack, and keep shooting. If it still doesn't chamber, take a mag and slam the carrier home through the ejection port. But don't sit there and diagnose the problem in a fight, bang on it until it works, or go to any other weapon, plan, idea, place. Maintain your gun and you don't need a forward assist.... and if you do, your gun might be about to blow up.. So, I don't need one on this gun. If I was tromping through a swamp, I might want one, but I'd really ask for an AK47 first! Notice in the above image that even the brass deflector has been milled out, nice.

The stock is a Rifle-Length from Smoke Composites. I went rifle length for a few more coils on the recoil spring, giving me just a hair more linearity in the cycle... and I wanted a longer pull with a full length buffer. This thing is very, very light and strong. I did have an issue though; there was no back-plate in the stock I received for the buffer to stop on. (where that urethane piece is on your buffer) I don't know if all of them are like that or just mine, but I machined and super-glued in a piece of carbon fiber to fix this. I emailed Smoke Composites, but did not get a response. If you don't make sure that your buffer (and carrier during recoil) stops the cycle, the AR will stop it for you by slamming the top of the gaskey on the stock thread embossment on the lower and break it; yes it happens. Because of the stock design I also had to modify the buffer pad. Not good for parts interchangeability but it's what I had to do to use this stock. I'd do it again too; this thing works great. If I could change one thing, it would be that the threads are cut on the stock. I would rather them to be rolled (stronger, the mil spec for buffer tubes is that the threads are rolled), and of course for them to fix the buffer stop problem. Buyer beware. I got the end plate from V Seven, it's titanium, because I wanted a quick release, and I didn't want a steel quick release engaging aluminum. If I wasn't going single point, I would have simply used the carbon fiber plate that came with the stock. The mantra is still "As light as possible, BUT STILL BET YOUR LIFE ON IT". Having to rely on equipment sucks anyway.

Buffer and spring (for now) are standard rifle weight. Carbine weight might not be a bad idea, but this thing is cycling great and the rifle is so light that if the rifle weight will do, I'll take it. The extractor spring is a standard Colt M4 spring, with black insert and a rubber D-fender o-ring. I'm using an Odin-Works melonited bolt carrier Standard M4 weight. Melonited because it is a surface treatment rather than a coating, and the bolt and barrel can be kept near the same hardness on the surface; and of course it's corrosion resistance. It really is smooth, and fun to touch. I don't know if it is a measurable performance advantage as far as lubricity, but it definitely feels smoother when operating the action by hand. I believe the bolt is a brownells melonited bolt. The firing pin is a Rubber City Armory Melonited (Nitrided) pin. I polished (using polishing pads for pen turning/making) the end of the bolt to get within .0005 of the center of the M4 firing pin protrusion spec. Did I need to? Na. I checked head-space with a no-go and a field gauge and was in spec. NO LUBE on the firing pin BTW, keep it as dry as possible. Lube gets blown in there anyway, and a greasy pin collects gunk, that can lead to light primer strikes, or slam fires. 10w30 on a cold day can be so thick that clean oil on the pin will prevent it from firing due to light strikes.

The trigger is an SSA-E from Geissele. If I had to do it again I might get something more fun, but the mantra here was a great two stage (duty gun) but still ultra reliable. I figure a trigger used by special forces must be good, they know more than me. It feels pretty good, and works flawlessly, but it's no competition trigger, and they'll tell you that. It should also be noted that it feels much better actually firing the carbine, then just dry firing.

I should also note that any AR build I've done, I've always gone for the center of any torque spec, or measurement. I have found it's a great way to build when you simply don't know the pros and cons of a spec! So far I'm really happy with my builds. I've got a rubber bumper installed (just set in) to keep the upper and lower from rattling; it doesn't effect anything else.

As far is ancillary equipment, I have a Bravo Company Ambidextrous charging handle, a B.A.D. lever from Magpul, and a Troy Ambi mag release. You gotta be able to operate your rifle from either side. Watch out for the Troy Ambidextrous mag release; the pin started walking, and I had to flare both sides of the roll pin to keep it in place (after that no trouble though). If I could do it again, I might go to the Raptor ambi charging handle instead of the Bravo Company. The Bravo pinches me every now and then. (both are 7075Al)

Update on the B.A.D. Lever, I trashed it, it strips it's screw and falls off. There are better options, like the WELDED Phase 5 Weapon systems EBRv2, nice!!!

I have a Trijicon MRO, 0 power optic, installed. It's perfect for a lite build, and FAST!

The sling is a Savvy Sniper Single/Double and it's the best thing I've ever laid my hands on. It is pretty heavy but it doesn't add much in the scheme of things.


As of 8/8/2017 I have takin the MRO off a few times just to use Thusla for different uses. To me clear the MRO is the besdt red-dot I've ever used, however, while the body of the device is forged 7075 (nice!), the threaded side of the rail mount clamp is not super, nor is the horrible torx hardware. I have replaced the hardware with high-quality allen bolts and safety-wired them, so I would not have to put so much torque on them, into the threaded clamp. I'm sure the wire is not needed, but it's piece of mind and it costs next to zero weight.


So how accurate is T-Doom? VERY! Click Here!

Where to next?

If you're thinking about building an AR for the first time, you want to go here: EVERYTHING AR
This is where you'll find build manuals and living documents of current technologies.

Back to