Sero Engineering Factory Tour (Makers of GM6 Lynx .50BMG rifle)

Dickson has shared another factory tour with us. This time he went to Hungary to check out Sero Engineering, the people how make the barrel recoiling GM6 Lynx.

Have you ever seen that really cool .50BMG bullpup rifle that shows the barrel recoil like a howitzer cannon after each shot and blows up anything in its sights on YouTube?

Perhaps you’ve seen the animated GIF image flowing around on the internet ripped from the full video. Did you know that the rifle, called GM6 Lynx, is made in Hungary?


To those who are not familiar, the GM6 Lynx is a portable anti-material rifle that fires either the .50BMG NATO cartridge or the 12.7x108mm Russian cartridge. It’s a semi-auto, bullpup design that weighs only 25 pounds empty. It features a unique barrel recoil technology that dissipates most recoil energy and the barrel can be retracted during transport or when the operator is in a vehicle. It does not feature the use of a gas piston like a Barrett semi-auto, instead it’s recoil operated. With a hit of a button the barrel extends and it is loaded and ready to fire in one second.

Here is another video showing how quick and easy it is to get the gun deployed and firing.

When the barrel is retracted the total length is only 36.5 inches which is truly exceptional for a firearm of this type.


It is usually equipped with a 29 inch barrel but there is a longer 36 inch barrel optional. Effective range is 2000+ meters with match ammunition. It is capable of sub MOA (minute of angle) accuracy with match ammunition and it uses match grade barrels. It uses steel magazines capable of holding total of 5 rounds.

Back in early December, I had the fortunate opportunity to travel to Hungary to meet Endre Szabo Jr., the general manager of Sero Engineering Ltd. and I was provided a factory tour of their newly built production facility about 30 minutes north of the Hungarian capital Budapest.

Hungary has a long history of producing various weapons, ammunitions and ammunition components dating back to the Austro-Hungarian era in the late 1800s. The famous Mannlicher M95 bolt action rifles that were made in Steyr, Austria were also produced in Budapest for the Austro-Hungarian troops in World War I. FEG (Arms and Machine Factory in English) was a famous producer of small arms, known for their quality Kalashnikovs as well as Hi-Power pistols. Unfortunately, firearms production was ceased in 2004 and the company instead produces heaters and air conditioners.

Writing as a long admirer of the .50 cal round, it has always been a personal goal to obtain a “50”. As a recent owner of a Steyr HS50 M1, my interest with 50BMG rifles has only increased. It’s like the ultimate precision rifle as the .50BMG is an extremely versatile round. I’m finally part of the big boys club.

In the automotive world, this is akin to driving a V12 powered car. This past Summer I had the rare opportunity to drive a beautiful 6.0 Liter V12 Aston Martin DBS which is more akin to a grand tourer rather than a true sports car. The sound of the engine was just so raw and addictive. Once you have driven a 12-cylinder car, you get to listen to the wonderful noise, feel the smoothness of the engine and available low end torque without needing to rev like a 4-cylinder motor. There is simply no going back.

I did not know what to expect with my visit other than the fact that the company is relatively new. The GM6 Lynx is similar to the Gepard series of anti-materiel rifles that originally came about in 1988. Endre explained that the development of the GM6 Lynx first started in 1999. The family owns various companies since the late 1980s as that was the earliest time when regular citizens were allowed to start and own private companies in Hungary. They have previous experience in manufacturing producing parts for military vehicles. Since his early childhood, he was fascinated with guns, cars and tanks. Over the years he has accumulated an amount of knowledge on design and engineering of firearms and vehicles. In fact, in his office he has all the service manuals for Soviet tanks such as the T-72 and T-55, etc. He was delighted to hear I drove a T-55A tank just last year in the town of Várpalota in Hungary. Unsurprisingly, he is a fan of nice cars – he showed me his 90s Mercedes Benz S-class and Lincoln Continental Mark VII (with the 5.0 Liter V8) project car that were both imported from Florida that is part of his collection. Guys will always be guys – we love their toys no matter which part of the world we are in.

Upon asking Endre who their lists of clients are, he pointed out that majority of the sales are to military and police units around the world. They have impressively recently received a large contract to deliver 800 rifles in the next 12 months in addition to the few hundred rifles that are currently being produced for various countries. He already has plans to expand the assembly area and acquire more machines to increase production numbers. He does receive civilian orders from Canada as well as from wealthy countries like Switzerland. The GM6 is approved for US imports, and the Canadian Importer, Tactical Imports Corp. will be looking at handling US sales in early 2017.

In the production area of the facility, he showed me the raw, unfinished rectangular aluminum blocks that were being fed into the CNC machines.


The aluminum were machined into pieces for the pistol grip as well as the lower receiver. Each piece was checked for tolerances in a separate enclosed room by a probe machine that can measure a 2000th of a millimeter.


Endre assures me that each manufacturing area is climate controlled at 20 degrees Celsius to ensure manufacturing of the materials are dimensionally accurate when the measurements were done.


At a nearby station, Endre showed me the steel magazines that were laser welded and the industrial caliper used to inspect the dimensions once they received the magazine body from the supplier. Due to the precise fitment of the magazine into the receiver, the cost of manufacturing the magazines is quite high and he assured me that they make no profit selling additional magazines to their customers. He said the future plan is to introduce polymer version. Polymer magazines not only will be just as durable but also will be much cheaper to produce. The cost savings will get passed down to the end users.

We proceed to the boardroom upstairs where Endre has a GM6 Lynx on the table. He told me that each rifle is to have a 5000 round guarantee which is quite impressive. The rifle is also capable of firing without any oil which is a benefit in desert environments. They submit the gun to a third party laboratory for military testing that involves a drop test, water submersion test and sand test. In addition to the Hungarian military standard, he had also submitted the rifle for testing with other countries as they have slightly different requirements. It’s interesting to note that one test rifle fired just a little over 6000 rounds before a malfunction occurred. That is a lot of loading rounds into magazines and magazine changes!

Endre pointed out to me this is a low recoil rifle. In fact, he was the person that fired the rifle at many of the demonstrations with various military and police units around the world. In one particular demo he fired 500 rounds in 7 hours without fatigue to his shoulder. The rifle slowly pushes against your shoulder instead of a hard slap and there is less recoil than shooting a 12 gauge shotgun.

Disassembly was also an ease and requires no tools. First the muzzle device needed to be unscrewed, and then a long but small diameter spring was released from the buttstock with a slight push.


Then, unscrew the nut up front holding the large spring running over the barrel. Once that’s done, proceed to unscrew the captive nut on the top of the buttstock. The upper receiver can then be lifted up which allows you to pull on the charging handle to remove the bolt assembly. The barrel will slide out and the field takedown is complete. In one of the army demonstrations, one soldier was shown how to do the disassembly and reassembly twice, and he was able to do that including removing and reinstalling the firing pin in less than 3 minutes.

It was clear that this beast of a rifle balanced naturally in my hand, due to the weight distribution of the bullpup design. I mentioned to Endre that the competition does not have anything close to their offering, but he was reluctant to go into product comparisons as he is also friends with many people working at these other companies.


Endre brought out the first serial production of the GM6, serial # 001 for me to compare the various improvements they have made. The difference between the two is quite dramatic.


The current rifle seemed to be much better made and overall more polished. In the original rifle, the charging handle was just cut from a steel cylindrical shape instead of the more refined, machined shape it is now. The picatinny top rail extends further out to accommodate night vision attachments and there are picatinny rails 3, 6 and 9 o’clock for attaching various accessories such as a vertical grip, laser, flashlights, etc.

In terms of factory options, they offer a scope protector made out of aluminum that protects the scope during transport or in case the rifle is dropped. It also functions as a carry handle as well as backup iron sight.


See the white dot? That is the front sight.


If that’s not to your liking, a lighter, nylon scope and muzzle cover is offered. In addition, they also make a backpack that is designed to fit the rifle for long distance deployment. Of course, a factory suppressor that screws directly to the barrel is also an option.


I raised the question about the ability to feed match rounds with heavy and long bullets. Endre showed me the box where it showed the rounds on the table were actually 770 grain bullet and after feeding the round into the mag, there’s plenty of extra space available.


It would make sense since the rifle is also capable of firing the 12.7x108mm Russian round which is longer by 9mm. He pointed out that the rifle only requires a quick barrel and magazine swap to change between the two calibers. This can be done in the field without tools.


The GM6 Lynx is a well rounded rifle that’s capable of various types of missions from close quarter combat to precision shooting over extreme distance. One major drawback similar to other bullpup designs is that it can only be fired right handed. The company did receive customers’ requests for a left hand version but currently there’s not enough demand to justify production.

In terms of future product development, they are currently working on a magazine-fed, semi-automatic rifle that shares the same long recoil technology as the GM6 Lynx but fires the much larger 14.5x114mm Russian round.


This round has twice the energy at 32,000 Jules than a .50BMG at 15,000 Jules with a 3km (1.9 mile) effective range. This round makes the .50BMG looks small! Interestingly, the 5 round magazine is parallel to the pistol grip. The prototype that they had shown me is quite light weight at just 17kg without ammo and scope. Most of the 14.5mm bolt action rifles in the market weight around 23kg (51lbs) empty. This is really a handheld artillery.

To round up the tour, I had mentioned previously to Endre that I love Hungarian dishes such as goulash and chicken paprikash. He took me to a local Hungarian restaurant and we ordered exactly just that. The goulash, not to be confused with beef stew, was delicious and so was the chicken. There are definitely many things to love about Hungary and there are a lot of reasons for anybody to come for a visit.


Thanks Dickson for sharing this. I want to shoot one of these badly. It is on my bucket list.

Nicholas C

Co-Founder of KRISSTALK forums, an owner’s support group and all things KRISS Vector related. Nick found his passion through competitive shooting while living in NY. He participates in USPSA and 3Gun. He loves all things that shoots and flashlights. Really really bright flashlights.

Any questions please email him at


  • daniel

    I’m skeptical about this, if only for the reason that with so many gun manufacturers in the US, someone must have tried this and concluded it wasn’t a good idea. This idea seems great, a shorter rifle with less felt recoil, but there must be some tradeoff.
    That said, if they can truly deliver on the promises, then they’ll have many customers, and I’ll be saving pennies to own one.

    • Gus Butts

      These have already been available in Canada for a while now.

    • iksnilol

      You really think American gun manufacturers are creative or innovative on an usual basis?

      • Michael R. Zupcak

        But, dude, there are bottle openers for your picatinny rail! What are you crapping on our great American innovation for? Do you even innovate, bro?

        • iksnilol

          Pffft, Israelis had bottle openers on their rifles before picatinny was a thing even. So much for thou innovation.

    • Phillip Cooper

      They are presently delivering rifles. I’d say it’s proven.

    • Bierstadt54

      If I could afford a 50, this would be my top pick.

    • Flounder

      Bro, Americans invented the long recoil action. And the short recoil action for that matter. But we just don’t seem to like expensive 50s anymore. We seem to use 338 lapua a lot more. Last I checked this rifle cost 15000? Although I think that was an estimated MSRP. Or what it goes for in another country.
      Unfortunately that means this monster, is one of the most expensive rifles out there.

      • Paladin

        They are $15,000 in Canuckistanian Pesos, and have been available here for a few years.

  • therealgreenplease

    I’ll take one!

  • GD Ajax

    An all black GM6 looks almost like an oversized Steyr Aug.
    They should make start making a conversion of their rifles in .408 Chytec before Desert Tech starts on their own 10mm semi auto.

    • Vitor Roma

      Came here to say that. This gun would be a sweet shooter in .408.

      • iksnilol

        Or .338 lapua.

        • Gary Kirk

          416 Barrett

          • GD Ajax

            An inferior ripoff of .408 CheyTec created so Chris and Ronnie Barret could make more money on a substandard product.

          • Dickson Ly

            Sero did experimented with the .416 Barrett round with success, but according to them there’s not enough demand to justify production.

        • Flounder

          That is what i was thinking would make the most sense. But Then my next thought was that they would have to scale it down to work with a round that was so much… Weaker… Not saying 338 is a slouch but it is like half the muzzle energy of a 50

          • iksnilol

            eh, still, if they scale it down they could get the weight to really manageable weights. I mean, I wouldn’t be surprised if a .338 lapua version weighed like 5 kg.

        • Dickson Ly

          There’s too much competition in the .338 lap arena.

          • iksnilol

            Not many semi autos in .338 as far as I done reckon.

  • Gus Butts
    • Dickson Ly

      If you look closely, there’s threads on the end of their can for the end user to thread on additional extension for more suppression.

  • Tommy

    “It does not feature the use of a gas piston like a Barrett semi-auto, instead it’s recoil operated.” Barretts do not have pistons :/

  • SP mclaughlin

    I’m pretty sure the Barrett barrel recoils as well.

    • Paladin

      The Barrett rifles use short recoil, while these use long recoil. The difference being that in the Barrett the barrel only recoils for a short distance while in the GM6 it recoils along the entire length of travel with the bolt locked.

  • PK

    “Unique barrel recoil technology”? I suppose you’ve never seen a Remington 11 or Browning Auto 5. It’s just a long recoil firearm.

    • Bierstadt54

      Very little is truly unique, but it is certainly unusual.

    • iksnilol

      Well, no offense, but those guns haven’t been made for like many decades and I don’t see many other guns on the market with the same concept. Even the modern auto 5 doesn’t use it.

      • PK

        No offense taken at all, what’s old is new again is a common theme. We’re near the apogee of cartridge firearm tech, reusing ideas doesn’t surprise me and can yield extremely pleasant results as in the GM6 Lynx, or the AR15 bolt from the Johnson system of the 1940s.

        • GD Ajax

          Some times the vision is there, but the tech isn’t. It’s the same reason we are seeing development in polymer cases and caseless technology.

  • gunsandrockets

    New life for an old operating principle.

    Long-recoil was one of the first types of successful mechanisms for semi-automatic shotguns and rifles. Eventually eclipsed by short-recoil and gas-operated mechanisms because of the inferior accuracy, greater weight and greater complexity of long-recoil operation.

    But when used in a high-end .50 caliber bullpup rifle, I can certainly see the advantage of long-recoil operation.

    • noob

      I’m interested in the secret sauce on what kind of guides or rails live in the receiver.

      According to the feature list for the weapon these rails must:
      1) keep the barrel true to the sights until at least the bullet has left the suppressor, to a level to allow hitting a materiel target at 1000m. This means very tight tolerances.
      2) operate without lubrication in the desert. This implies both tight tolerances AND generous clearances for consistency and low friction. There could be special treatments and materials involved.
      3) long enough for continuous recoil operation without having the mass of the barrel bottom out against the receiver.
      4) short enough to make transport mode with a retracted barrel not be defeated by the length of the receiver.
      5) wear and corrosion resistant so the weapon stays accurate over time.

      The internal action guide rails, that we saw the mounting holes for in the receiver blank but never saw an image of, the rails are the true innovation.

      Also the trigger linkage on any bullpup precision rifle is always interesting too

      • guest

        Though the rails are not shown, outside wear on the barrel on one of the picture tells me there are “rings” holding the barrel, not rails. Hence the tight tolerances are indeed present. Even if those geniuses used say brass rails with deep slots dedicated to avoid being jammed by any contamination it would still mean wear and eventually looseness. The only thing I can think of is that during the “last part” of forward movement the barrel is, at several separate locations, being jammed into a conical part of the receiver. Conical in order to center it when it’s loaded and ready to shoot. Then except that position the barrel does not need to be either tightly within the “rails”, neither does it need to be centered.
        But I’m just guessing here.

  • kyphe

    Hmm traditionally the long recoil system in rifles like the Remington 11suffered from excessive recoil due to all that moving mass of barrel hitting your shoulder

  • Blake

    Köszönöm Nicholas, I’m a big fan of the GM6 Lynx.

    None of my Hungarian friends knew about this awesome rifle until I showed them the vids of block-smashing at 1km.

    • Dickson Ly

      That’s likely because .50BMG rifles (and larger calibers) are banned from civilian ownership in Hungary.

  • mechamaster

    I Imagine that the 25 x 59mm “Grenade Sniper”version of GM-6 Lynx…
    The long-recoil could mitigated the recoil better than Barret XM109 Short-recoil system.
    Plus that compact size when the barrel is retracted in transportation configuration.

  • MisterTheory

    I want just because I think it looks awesome to see the barrel cycling back and forth like a howitzer.

  • guest

    14,5mm…. in case an APC or an early WW2-vintage tank shows up.

  • mazkact

    Love it. I do wonder about accuracy. With a long recoil design there must be a certain amount of barrel “play” relative to the receiver which the scope is mounted to. Very cool in any case.

    • noob

      🙂 i just finished typing a comment about how we saw mounting holes inside the receivers but we never saw an image of the action guide rails that would be installed on those holes.

      I guess we would need to buy a weapon of our own to get a camera down there to see how they addressed the truing of the barrel and the sights in a long recoil rifle

  • dltaylor51

    I wish they would make that recoil absorbing system that would retro to my AR-50.