A .50 BMG for Everyone: Serbu’s Lightweight, Single-Shot RN-50 — Full Review

This week, I drew the assignment of shooting a light weight .50 BMG. For those who aren’t familiar with this powerhouse cartridge — the .50 BMG and light do not belong in the same sentence — certainly if you also include single-shot or bolt-action.

A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

The RN-50 is a unique design from Serbu Firearms, Inc. It is a modified break action rifle with a threaded breech. Photo Courtesy: Serbu Firearms, Inc.


A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

The author found the muzzlebrake effective during testing.

  • Type: Modified break-action with a threaded breech
  • Chambering: .50 BMG (tested); .50 DTS
  • Barrel Length: 29.5 in.
  • Overall Length: 39 in.
  • Trigger: 8 lbs. (tested)
  • Weight: 17 lbs.
  • Sights: None
  • Finish: Magnesium phosphate and hard-coat anodized
  • Capacity: 1 rd.
  • MSRP: $1,199
  • Manufacturer: Serbu Firearms, Inc.

Background Information

A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

The author’s test rifle was chambered in .50 BMG. However, Serbu Firearms also offers models in .50 DTC.

The .50 caliber in question was the RN-50 from Serbu Firearms, Inc. This Tampa, Florida based company is one that I have a great deal of respect for. The founder Mark Serbu is a mechanical engineer that is best known for producing the BFG-50: a .50 BMG caliber, single-shot rifle. Serbu Firearms has always strived to produce high-quality firearms that are either: cool, unique affordable and specifically engineered to stick-it-to-the-man. The RN-50 accomplishes all four. 

My guess is that the development of the RN-50 is the belief that everyone should be able to afford a .50 if they want one. The market is never wrong, and this is America damn it. If such a thing exists, the local citizenry should be able to buy it. We tossed off the yolk of monarchy if Uncle Sugar can have something, by God, we all should be able to have it. The big problem with .50-caliber rifles is that they’re typically cost prohibitive.

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The pressures produced by John Moses Browning’s greatest gift are enormous, and there are some places you just can’t shortcut the process. Even a traditional bolt action needs some “beefing up” to handle this monster of a cartridge, and that means more machining time.

A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

Serbu Firearms offers a variety of barrel lengths. Photo Courtesy: Serbu Firearms, Inc.

A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

The RN-50 is a 17-pound, .50 BMG single-shot with an MSRP of $1,200.

Enter the RN-50

Serbu looked at this problem and solved it in a brilliant way. The RN-50 is a single shot that you load through a breech plug. Obviously, this is not the quickest reload but gets the job done. An extremely large thread pitch ensures enough metal is present to handle the pressure of the .50 firing. The trigger group is mostly AR-15, with an oversized hammer to reach the firing pin that is embedded within the breech plug. The buttstock is attached with an AR-15 castle nut and is interchangeable with your favorite AR parts. There is so much metal removed, there is nothing over the top of the trigger group. The barrel looks suspiciously like the same contour as an M2 machine gun, but there’s nothing wrong with that. If it isn’t broke, don’t fix it. Sgt. Carlos “White Feather” Hathcock set the longest kill of the Vietnam War and made his famous 1-mile shot with a scope mounted on an M2. They are nothing if not accurate, and they will take all the abuse you can throw at them. At the end of the RN-50 barrel sits a simple but effective muzzlebrake. It comes standard with a 29½-inch alloy steel barrel with 18-inch, 22-inch and a 36-inch heavy barrels as options. The RN-50 features a 1:15-inch button rifling and the chassis is a heat treated steel and aluminum construction. With an MSRP of a little less than $1,200, it’s a hard option to beat for those looking to get into the .50 caliber market.

A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

The RN-50 features a unique breech loading design.

A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

The author found the RN-50 to fire reliably and mounted a Steiner M5xi Military 3-15x50mm. The Steiner M5Xi Military held up to the punishing recoil of the .50 BMG, and the RN-50 produced 1-MOA groups at 100 yards.

It’s a classic Serbu, that can be had throughout the United States. Our test model was chambered in .50 BMG, but for those living in the Peoples Republic of California, it is also available in .50 DTC. What is .50 DTC exactly? In layman’s terms, the .50 DTC is a round specifically made to get around the red tape of places that have banned .50 BMG. The .50 BMG (Browning Machine Gun) or 12.7x99mm NATO was developed in the late 1910s for the Browning .50 caliber machine gun. The .510 DTC, also known as the .510 DTC EUROP was a French rifle cartridge that was developed to comply with firearms legislation in Europe that regulated .50 BMG. When the .510 DTC was brought over to the U.S., it was modified to the .50 DTC. The .50 DTC is nearly identical to the .50 BMG but you cannot fire them in the same chamber.

A .50 BMG for Everyone: Serbu's Lightweight, Single-Shot RN-50 — Full Review

The Hornady 750-grain .50 BMG A-MAX bullets fired reliably and printed a 1-inch group at 100 yards.

Range Performance

I am not going to lie to you, this gun has punishing recoil in a light package and is not the most fun to shoot. At 17 pounds, it is a full 10 pounds lighter than a McMillan TAC 50. It is the lightest .50 single shot that I have ever fired. Without the muzzlebrake, I don’t think you could fire this thing without body damage resulting. I have burned up some magnum rifle ammo in my day, so this isn’t new guy jitters. During testing, I shot less than 40 rounds, which is not a lot. Still, it performed like it said it would. My three-round post-zero group was exactly 1 inch, so it meets a 1 MOA standard. I am actually amazed by that, considering how hard I was flinching after the first two rounds. This is not something you want to shoot on a daily basis. But if you are in need of a .50, and you don’t have a lot of money to spend, it gets the job done. Given the price tag attached, I am extremely impressed.

This rifle is a testament to American ingenuity, and I give it 5 stars, but please don’t make me shoot it again.

For more information about the Serbu RN-50, click https://serbu.com/products/rn-50.

To watch Clay’s interview with Mark Serbu at SHOT 2017, click https://www.gunsamerica.com/blog/serbu-cqb-50-cal-super-shorty-mossberg-bunch-cool-shit-shot-show-2017/.

For more information about Steiner scopes, click https://www.steiner-optics.com/riflescopes/miltary/m5xi-military-3-15×50.

For more information about Hornady ammunition, click https://www.hornady.com/ammunition/rifle/50-bmg-750-gr-a-max-match#!/.

To purchase a Steiner scope on GunsAmerica, click https://www.gunsamerica.com/Search.aspx?Keyword=steiner.

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  • Paradise Road May 22, 2021, 3:14 pm

    …cross between a zip gun and a pipe bomb…now thoroughly proven…BOOM ! …

  • Jim Xoch April 30, 2021, 12:52 am

    To rain on this 5-year-old parade, large thread pitch = less strength.

  • Dj Thompson February 23, 2021, 12:11 am

    Mark Serbu runs a great company with respectable principles. The RN 50 was inspired by Royal Nonesuch a youtuber who also enjoys homebuilt platforms. Mark decided to help with Royal’s idea for a ” as simple as possible 50bmg platform and liked it so much decided to put it into production. All honesty it’s a very accurate and rugged built platform. With it’s breech loaded design it creates a even force applied to the shell which is technically better for accuracy then a bolt action so it’s actually a benefit over semi-auto and bolts gun with the disadvantage of slower follow-up shops. He also offers semi-autos said to be built simpler and more accurate then barrets platform not to mention a great affordable bolt operated single as well. The re-coil is not that bad for a 50. I really didn’t think it was that bad honestly. It’s definitely no .22 though. .. but manageable. I was so impressed that I ordered one after shooting a friend’s RN-50. I have shot a semi-auto Barrett as well as a bolt Barret and Taclite. The RN-50 has been on the market for awhile now and has held up well. No failures and the screw on cap is also blocked by the receiver once the actions closed so it’s some peace of mind if your worried about it being a threaded breech. They been out for many years now with no failures. Id’ take his semi-auto over a Barrett anyday even with a unlimited budget as far as commercial guns go.

  • mka August 1, 2017, 8:50 am

    Reminds me of the hype when Dirty Harry had the “worlds most powerfull handgun”. The hype that followed
    caused every gun squirrel to run out and buy one. Worthless piece of plunder.Designed with the gun squirrels in mind.

    • jim August 1, 2017, 5:39 pm

      No hype or squirrels. No plunder either. Fun to shoot. I have one and don’t fit the profile you suggest. Inexpensive way to shoot 50 bmg. More of a bucket list thing for those who just want to pull the rifle out a few times a year and feel the boom.

  • Brian August 1, 2017, 1:32 am

    One thing that I really think needs to be pointed out: For safety’s sake, ALWAYS cock the hammer and engage the safety BEFORE closing the action with a round in the breach. NEVER attempt to cock it after loading a round and closing the action. If you were to do so, and the hammer slipped, it could be disastrous on both ends.

    • jim August 1, 2017, 5:33 pm

      The hammer has two cocking positions. Just off the firing pin and fully cocked. The safety is the same as a AR-15. So what you are saying is correct. The gun is cocked to the first position and the safety is engaged. Then you can open and close it (or take it apart) as needed. Very obvious once you start using the gun that this is the default process.

  • Franks62 July 31, 2017, 11:26 pm

    Serbu Firearms has always strived to produce high-quality firearms that are either: cool, unique affordable and specifically engineered to stick-it-to-the-man. The RN-50 accomplishes all four.

    There’s only three items in that list unless the affordability is supposed to be part of the list. Either way this, along with nearly every article on this site, really needs some editing. That criticism aside I do enjoy most of the content produced by the site’s staff.

  • George July 31, 2017, 11:12 pm

    If you’re going to review the gun, you need to research it FIRST. It’s called the RN after Royal Nonesuch who made the first one and has a dedicated You Tube channel. Serbu is making them but this crazy kid came up with the design. How about you employ someone with some form of training in real journalism who can do a modicum of proper research? Jeez.

  • N6JSX July 31, 2017, 7:19 pm

    I look at the recoil pad/stock and wonder how one will not get rotatory-cuff problems after firing 10 quick (3min) shoots. You know I see all these fancy statistics and data but for one thing “recoil pressure” upon the shoulder. Maybe that needs to be a data factor in all these gun reviews.

    Sure looks like a home protection gun to me that everyone needs to buy – not.

  • Mike Watkins July 31, 2017, 4:51 pm

    This is very appealing because of my limited toy budget. Unfortunately I have SOOOO many things on my want list, and a 50 cal isn’t really at the top.

  • Just1Spark July 31, 2017, 3:41 pm

    Or, for less than double the price, http://www.statearms.com/rifles/shorty.php

    I wonder, is the breech plug considered the receiver?

  • Jim July 31, 2017, 11:10 am

    I have one of these Serbu RN-50s. I shot 9 rounds and let someone else at the range shoot one so I could see what it looks like. After sighting in, I put two rounds an inch apart at 200 yards. That was enough 50 BMG shooting for the day. Pulled out the 300 win mag after that. I put a PRS stock on it for cheek adjustment and a little more weight. Used a Bushnell Elite Tactical scope to handle the kick. Because the breach is forward of typical rifles, I opted to use AR 15 mounts in reverse to get the scope back a bit. The stock and scope can be re-purposed in between use of the 50 BMG. Harris bipod holds up but I am careful not to abuse it beyond the firing of the rifle. The gun breaks down into two pieces that are easily handled and cased. Just remove a single clevis pin. I would buy it again as it is a relatively inexpensive way to shoot a 50 BMG. If more funds are available I would consider going for a semi auto 50 BMG. Wear plugs and muffs!! Warn other shooters nearby that you are going to shoot this thing.

  • Shooby July 31, 2017, 9:12 am

    This thing has been out for a while…get on your game with what’s going on in the Tampa Bay area….serbu makes a lot of nice firearms

  • Michael July 31, 2017, 9:11 am

    I’ve always wondered if you could beef up and weight the buttstock to add more mass to the gun and reduce the felt recoil. In this example, you could machine a lead insert to fit snugly into the triangle and easily add 5 or 6 pounds. Or mold it to fit over the entire buttstock and add a few inches of lift for a better cheek rest, and perhaps add close to 20 lb. You wouldn’t want to go prancing through the field with this, but for fixed shooting, you might have a lot more fun and be able to use your right arm the next day.

  • Dr Motown July 31, 2017, 7:33 am

    How will that open action hold up to dirt, sand and grunge?

    • Richard Downing July 31, 2017, 10:20 am

      It’s hard to believe you asked that question it’s not a combat rifle. It’s a single shot fun gun.

  • Don Heher July 31, 2017, 7:30 am

    You don’t get much to it for $1,200
    … looks like a single shot.. single action pistol with an extended barrel.. even though it reloads a little faster than 1860 50 cal ..

  • roger July 31, 2017, 6:30 am

    Not a bad deal and a great price point. I’ve a GEOAZ 18″ shorty and my recoil is about same as a 12 gauge. The longer the barrel the more felt recoil. However it takes earplugs and a clam as they are loud. The compression is brutal also so I wear goggles. The muzzle brake looks ineffective on the Serbu. A better brake makes a big difference. 50’s are fun to shoot.

  • kk July 31, 2017, 4:05 am

    is the recoil much worse than 12 gauge pump shooting 3.5 ” magnum ?

    • Jim July 31, 2017, 11:17 am


      • Jim July 31, 2017, 11:21 am

        I added a softer pad to the PRS stock I put on it but the overall kick is like the 3.5″ mag.

  • Brian Coughlin July 31, 2017, 2:52 am

    It was supposed to be $800

    • SteveK July 31, 2017, 6:23 am

      Supply and demand

    • Dean July 31, 2017, 7:12 am

      The $800 price was the original intent, then became the early bird special.
      I was hoping to get that deal but just not enough money at the time. It’s a .50 BMG…… for $1200.00

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