Introduction

Many of you are aware of my affinity for Desert Tech rifles, and if you are reading this you’ve likely seen much of my content about the various rifles. Today I am diving down another custom project similar to one I’ve done in the past. I made a custom barrel for my MDRX in 6mm ARC years ago, and today I am bringing you the story on how I went about making another custom, my Desert Tech WLVRN 6mm ARC project.

Because of the extremely satisfying results with my MDRX, I became quite fond of the 6mm ARC cartridge and have since gotten more of them. It was also a natural choice for me when I got my Desert Tech WLVRN, of course this would again require me to make my own. Today I’ll go over how that went.

The Desert Tech WLVRN

The Desert Tech WLVRN is the latest generation semi-auto bullpup, a direct descendant of the MDRX. Both of them being multi-caliber piston operated carbines. They share a great deal of parts and features, but they are also very different. The barrel mounting system is different, as are the barrel extensions, bolts, receiver and more. Perhaps the best difference between the two in my opinion, is the larger clamping-surface that holds the barrel. Part of that is because the trunnion is machined into the aluminum receiver, getting rid of the steel barrel block. Additional other steel parts were also removed, greatly reducing the weight of the rifle. The machined-in trunnion also makes the WLVRN return to zero when switching barrels. This was something aspired to by the MDRX but was never consistent.

I bought my WLVRN initially setup as a 20-inch .223, which was awesome. It shot very well, and even with the longer barrel it felt lighter than my shorter MDRX. But I wanted more, I wanted the 6 ARC performance. Which in my opinion felt kind of like a 5.56 that shoots like a 6.5 Creedmoor.

The 6mm ARC

Hornady has put out a bunch of new calibers over the past few years, and the 6mm Advanced Rifle Cartridge (ARC) is one of many. The ARC boasts a very efficient design that gives impressive performance from AR15 platforms or micro bolt-actions like my Howa Mini.

The ARC can push 105 grain bullets at near 2800 FPS, which is still doing over 2000 FPS at a quarter-mile away and still carrying over 1000 lbs of energy. For comparison, thats much faster than a good 77 grain 5.56 load, and double the energy. And at 1000 yards, the disparity is just as impressive, not that I’d like to catch either of them. The 6 ARC can be fired from the same sized actions and magazines as the 5.56, so this ballistic advantage is enticing.

My former experiences with the 6 ARC in my MDRX and Howa Mini were very impressive, both from a target shooting aspect as well as hunting big game. We’ve killed several deer and antelope using the same 105 Hornady BTHP. This led me to be even more enthusiastic about an ARC for my WLVRN. Since my MDRX is a little heavier, and I already have bigger caliber conversion kits for it like 308, 6.5CM, and 450BM, I figured I would keep the WLVRN more of a smaller caliber rifle. The added accuracy benefits of the WLVRN also seemed like a better platform for a DMR type rifle.

Down the Rabbit Hole

Baseline

I started this project by contacting my long-time friend and gun-plumber at ES-Tactical. Despite his not wanting to get involved into another oddball project, he agreed to cut me a twenty-two-inch barrel from a K&P blank. It was a totally different profile than a typical WLVRN barrel, aside from a heavier profile I also spec’d a different gas block position further down the barrel.

Once I had the barrel in hand, I wanted to try something before it was even finished. I torqued down the barrel extension with some thread-locker, and headed to the range. With no gas block or piston operation, I wanted to see how accurate the barrel shot. So I fired a couple groups, operating the rifle manually like a straight-pull action. I was astonished to see that shooting my 105 grain handloads at 100 yards, the WLVRN put ten shots into just over 1/2 MOA. Something I wouldn’t have believed had I not shot it myself.

My reasoning was to see how much the rifle’s accuracy was effected by the gas operation once installed. Which was my next step.

Machining

It was time to make some metal chips of my own. I drilled a gas-port in the barrel and pressed the gas block down snugly. I figured I would just use the same gas-valve that my 20″ 223 barrel used and see if I could get it to work on one of the settings. But before I got that far, I would need a custom piston. Having moved the gas block towards the muzzle of the barrel, would require adjusting the length of the gas piston accordingly.

You might be asking yourself why I moved the gas block at all. The reason is to get a better purchase of the gas flow. By moving the gas block down the barrel towards the muzzle, the operation of the action is delayed slightly. This allows the bullet to exit the barrel long before any action movements, as well as allowing the gas-pressure within the barrel to decompress some. This makes ejection and extraction less stressful on both the rifle and cartridge case. There’s also an argument to made for barrel harmonics and accuracy as well. Timing the piston operation can greatly enhance accuracy by changing the way the barrel whips as the rifle reloads itself.

Once I had my custom piston ready, it was time to see how the rifle would function. This would require some trial and error, going through a variety of malfunctions tuning the gas flow until we found a happy medium. Luckily, my gas valve selection was close enough, which meant it was time to go back to the range. An unfortunate consequence in both the MDRX and the WLVRN was significant damage to cartridge cases when the rifle didn’t eject them properly.

First Range Trip

Accuracy

It was time for the first real range trip, with a fully functioning WLVRN. This trip was actually into the mountains and not the range, but I prefer the mountains over the range anyways. It would allow me to see how the rifle performed at distance as well.

My initial accuracy test were okay at best, mainly because I hadn’t anticipated for the weather. It was cold and snowing with some blustery wind thrown in, and to add some pressure it was getting late so I rushed it more than I’d have liked.

Even so, the WLVRN printed some barely sub MOA five shot groups. Later testing would prove even better. Most of my testing was done using a suppressor, my Anechoic Anechox 35 which made the rifle very tame and pleasant to shoot. I also shot it using the Yankee Hill Machine Turbo T3 which was better in some aspects I’ll detail below.

You can see from my additional testing, typical groups from the 6 ARC WLVRN average around 3/4 MOA. While the better groups would shrink as small as 1/2MOA. I am fairly confident this had more to do with me than it did with the WLVRN.

Long-Range

Just because I am incapable of not trying, I stretched the 6ARC out a ways to see how it did at some longer distances. We shot at 715 yards, and 430 yards in some pretty gusty wind. At 715 yards I held about 1.2 MIL into the quarter value wind and was very impressed with the impacts. Not only were they very consistent, but they really hit with some authority.

While shooting at the 430 yard-line, I aimed at a small patch of snow in some dirt. I can’t imagine the snow patch was much bigger than a can of tuna, and every shot from the WLVRN would have sent Starkist fish everywhere. I was really getting excited about this rifle’s potential.

Shooting this same load in my MDRX has proven to be very effective at distances as far as 1000 yards away. Taking varmints that far away is a fun and challenging venture, and with the same load my wife took down an antelope at just shy of 500 yards.

Additional Testing

Long Op-rod (pending)

Because I’m a bit of a tinkerer, I figured I would also try something else. My longer piston worked fine, but I also explored another option. Using a standard length piston, and an extended op-rod (the stainless rod that goes between the bolt-carrier and piston) was another option. By adding additional length to the op-rod, I would get the same effect as the longer custom piston. But in addition it would add more weight to the reciprocating mass of the bolt carrier. This would also help buffer the operation some, which I wanted to proof out. That way I could see which of the two approaches was more effective for reliability and accuracy. Come back for more on this development later…

Gas Refinement

I have no doubt that moving the gas block further down the barrel definitely helped with the function of the rifle. It likely reduced chamber pressures during extraction, and helped counter some of the barrel movement that has made accuracy a challenge with other similar variants. It also made it impossible to adjust the gas valve without removing the handguard, but I never cared about that feature anyways. I always shoot suppressed, so I set the valve and forget it.

That said, I think the significant increase in accuracy over a factory conversion kit has as much to do with the barrel contour as it does the gas block perch. The thick barrel is much stiffer, it actually barely fits in the chassis, I had to shorten the two handguard screws to prevent them from pressing against the barrel.

I also like the additional two inches of barrel, this surely helps me get as much velocity as possible out of the 6 ARC. And still gives me the compact handling bullpups are famous for. The only downside of course is weight, the added barrel diameter and length adds a fair amount. But this too is something I don’t mind dealing with, I like the accuracy over the light weight.

Suppressor Compatibility

Much of my shooting was done with the Anechoic Anechox 35 suppressor, which worked great. But since I didn’t have quite the precise ability to drill gas-holes in the thousandths of an inch, it seemed a little more challenging to get the gas flow just right. I did find that by using a different suppressor with a little more backpressure helped get just the right amount of gas volume.

I installed my YHM Turbo T3, which is a 5.56 suppressor. The tighter bore of the T3 added some backpressure, I assume that the traditional baffle construction of the T3 also had something to do with it as well. Disclaimer: I cannot recommend using a 5.56 suppressor on a 6mm cartridge, do so at your own risk.

That said, the addition of the T3 seemed to get me to the perfect operation for the rifle and the 6mm ARC cartridge. It greatly enhanced reliability and consistency of the operation, and it sounds great too! I think its safe to assume that any similar suppressor would have provided a similar outcome. Changing suppressors to get the optimal performance from a rifle is nothing new.

Ejection

Ejection of the 6 ARC case was predictable, the port is plenty big since it can accommodate 308 sized cases. I did switch out the polymer ejection port to the older MDRX style aluminum model, as they are a little tougher.

Lessons Learned

There is always something to learn with these projects. I for sure still like the 6mm ARC, perhaps even more so now because of my WLVRN. It has turned my little green wolverine into something quite a bit more mean. I still have the low recoil and efficiency of small cartridges, but significantly more downrange energy. Though if I did it again, I think I would have gone with a slightly lighter contour on the barrel. And probably fluted it as well, just to keep the WLVRN as light as possible. The accuracy from this combination makes the rifle more than suitable for my hunting purposes, both big game and varmints will soon succumb to the WLVRN and its 100 grain bullets in the next few weeks.

I’m sure I’m not the only one imagining the possibilities with this rifle; An accurate (sub-MOA) semi-auto rifle fed by 20-round magazines, with a kill envelope arguably to 1000yds, that weighs in under 11 pounds and 36.5-inches long with a suppressor…

[1000yard stare intensifies…]

That is not to say that these projects are for everyone. You absolutely must be some kind of a tinkerer, with a mechanical inclination. There is plenty of headache and challenge involved in a project like this. And theres always the possibility that your result isn’t as reliable or great as you’d hoped after spending a good amount of money. So temper your enthusiasm and expectations before considering a project like this. As always, I will update this with more information as it develops so make sure to follow me for.

-CBM