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50 Beowulf AR-15s: Everything You Need to Know

50 Beowulf
July 13, 2021 Edited May 13, 2024 42995 view(s)
50 Beowulf AR-15s: Everything You Need to Know

If you’re in the market for a hard-hitting brush gun that can tackle virtually any North American wild game you’re likely to encounter – whether it’s whitetail and wild hogs or bears and bull moose - look no further than an AR-15 chambered in .50 Beowulf.


Hunting/Self Defense Application

Introduced in 2001, .50 Beowulf was the first of the big-bore AR-15 cartridges to hit the market, and while manufacturers have since taken advantage of the platform’s legendary versatility to chamber ARs in .458 Socom and .450 Bushmaster, among others, the .50 Beowulf is still hard to beat when it comes to punching through dense foliage and heavy cover at short to medium ranges.

The round is also well-suited to tactical applications in urban environments, which is why it has seen relatively widespread adoption by military and law enforcement personnel who need a tool that can easily penetrate windshield glass, auto body panels, and body armor without any noticeable deflection.

12.7x42 ammo


Caliber Dimensions

The .50 Beowulf cartridge features a tapered straight-wall case based on a lengthened .50 AE case, but one of the first things you’ll likely notice when picking up one of these rounds is the heavily rebated rim, which fits a bolt head designed for the 7.62x39mm cartridge. It’s a strange-looking combination, but don’t let the looks fool you – this round performs flawlessly, and that same case design, along with the plentiful availability of .50 bullets, make this cartridge a reloader’s dream. [50 Beowulf's cartridge size is 12.7x42, and due to copyright constraints from Alexander Arms, many manufacturers (including Bear Creek Arsenal) will refer to their uppers and barrels as 12.7x42. 50 Beowulf and 12.7x42 refer to the same thing, however.]

50 Beowulf Magazine


50 Beowulf Compatibility & Magazines

But for my money, one of the best features of the .50 Beowulf cartridge is just how easy it is to transform your AR with a simple upper swap – any mil-spec lower will mate to a .50 Beowulf upper with no issues. Your existing 5.56 magazines will work just fine, though they’ll only hold ten rounds in a single-stack configuration thanks to the hefty case size. [We recommend using dedicated 12.7x42 magazines, however, for optimal reliability.] That means that if you already own an AR (and if you’re reading this, you probably do), one of our Bear Creek Arsenal complete uppers can have you slinging .50 downrange for under $350! [As always, we recommend tuning the upper to the lower by making adjustments such as adding a heavier buffer/spring to reduce recoil.]

50 Beowulf shop now button


50 Beowulf Recoil

Ergonomically, an AR chambered in .50 Beowulf doesn’t feel all that different from one chambered in 5.56. It’s certainly a bit heavier, but you’ll appreciate that extra weight when it comes time to pull the trigger – the heavy barrel and muzzle brake keep muzzle climb to a minimum and make the recoil much more manageable, though a touch more forward lean in your shooting stance will help, too.

In fact, assuming you’ve got your shooting technique squared away, felt recoil will be quite similar to shooting 12-gauge buckshot. [You'll want to add a heavier buffer spring to minimize recoil; we recommend an H2 or H3 buffer for our 12.7x42 AR-15 complete uppers and rifles.]

50 Beowulf



In terms of ballistic profile, the best point of comparison is the venerable .45-70 Government. Most .50 Beowulf ammo you’ll come across falls in the 300-400 grain range, and even at the very low end you’re still looking at a muzzle velocity of nearly 1900 fps, which translates into 2,300 foot-pounds of energy. In other words, it hits hard.

And like .45-70 Govt., you can expect some pretty dramatic drop and loss of velocity at long ranges, which is why .50 Beowulf is much more suited to shooting inside of 250 yards. You aren’t going to get sub-MOA precision out of it, but if you’re like me and do a fair bit of hunting in places with plenty of thick brush, there is a lot to be said for a big-bore, magazine-fed, semi-auto rifle that can put a hog down with a single shot while still allowing for fast follow-ups when you encounter a runner or multiple targets. [To learn more about hunting with an AR-15 and AR-10 see our guide about the Best AR-15 & AR-10 Calibers for Hunting.]


Fun to Shoot

Last but not least, there’s one thing about .50 Beowulf that simple numbers won’t tell you: it’s just plain fun to shoot something with this much power behind it. It’s a real thumper of a round, and when you start putting lead downrange, don’t be surprised to find other people wandering over to find out what exactly it is that you’re shooting. Whether you’re just punching holes in paper or if you’ve got some big game hunting planned, a .50 Beowulf upper is an excellent way to turn your AR into an affordable, hard-hitting beast of a rifle.

[We'd like to extend a huge thank you to Eric Shattuck for his hard work on this article. Check out our other helpful content like infographics and firearm guides.Comment what caliber you would like us to cover next below!]

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July 21, 2021
Clyde Lewis
July 23, 2021
You would have to buy a .50 BMG rifle. You cannot convert a standard AR platform to handle the pressures.
December 5, 2021
Two different animals there. Like trying to convert a Ruger 10/22 to fire .223. Safety Harbor Firearms makes a single shot and side-feed upper that fits & functions on a AR15 lower. Caution - on the mag-fed upper, a lotta bad malfunctions happened (kabooms) and early versions had all kinds of issues due to bad metallurgy. If you get a .50 Beowulf/12.7x42, enjoy it for what it is... a 100-200 yard, lightweight implement of destruction that allows you to take down ANY game in NA as well as defend yourself against vehicles up to a light semi truck or T-Rex! Oh yea, find a cheap source for cinder blocks... any less a target just doesn't do it justice!
Barry Wood
September 19, 2022
33,000 max psi
Edward Saul
October 13, 2022
Impossible! But there is a guy in "Youtube" that has been trying to build a AR.BMG for years now. Personally I dont see the point in that the recoil will be so bad that no man could shoot but 1 round at a time anyhow and shy of it being a anti-airstrike gun mounted {that they already have} would be its only practical purpose.
October 13, 2022
In order to fire a 50bmg, you will have to get a 50bmg upper for your ar15 lower, they are out there, good luck.
Jaime Espinoza
May 13, 2024
Just an update of that guy trying to make an ar15 / 50cal. It took him 8 yrs. to complete his monstrosity! But it was Really awesome, you got to check out the updated video!
July 21, 2021
December 5, 2021
YES... a simple barrel replacement is all you need but I've found getting a barreled upper and using existing BCG a simpler way (also allows you to go back to 7.62/.308 easily). Best bet is get upper and matched bolt for accuracy (it will work in 7.62/.308) and keep original bolt as a backup.
Poppa Phillip Stoffer
October 14, 2022
buy the 6.5 upper and save yourself some grief. I have found that doing a barrel swap just wasnt enough as I just refused to discard or sell off good hardware. every time I want a caliber, I get a new upper, I have 3 ar15 lowers, 1 pistol, 2 rifle. 2 ar10 lowers both rifle, got a ton of uppers. only one I dont have is a 12 gauge. Ive got a dedicated Tristar with a couple drums for that. Have Fun !
Lawrence Zagranis
August 24, 2021
Getting the 12.7x42 barrel in 18" what are the requirements for the Muzzle threads and gas block?
December 5, 2021
49/64-20 on the muzzle, unsure on gas block (should say in the Bear Creek webpage). Mine, an early AA Mil contract 16" upper with flash hider, doesn't recoil bad at all. Slightly sharper than an FAL but slightly less than a 20 gauge shotgun with an H3 buffer in the lower. I like the kick... lets you know you just sent 2500-3000ft/lbs energy downrange! ;)
Matt Tomlinson
September 25, 2021
I just purchased a 16" barrel 12.7x42 from you yesterday (the 299.99 sale) and was looking at muzzle brakes for looks and to reduce recoil. the timber creek heartbreaker is looking very attractive, but I am also looking at the tanker style. Before I can order a new muzzle break I need to know what threads are on my upper, can you answer that question for me, please?
September 27, 2021
The thread pitch for the 12.7x42 barrel is 49/64-20.
December 5, 2021
Oh yea, no real advantage to the 18" over a 16" since it uses faster burning pistol powders to push that fat-assed slug.
December 5, 2021
LOL! Just realized OP posted a year ago to the day. Well Lawrence, hope you got your Beo and are enjoying it.
February 27, 2022
Is the gas system on your 12.7x42 (50 Beowulf) completed uppers optimized for that cartridge or are they standard 5.56 NATO gas system specs?
Bob Winney
March 23, 2022
I have a BCA 12.7x42 and love it. I killed a bull elk and a whitetail doe with it this last fall. The rifle I built is using an A2 style fixed stock (I hate collapsible stocks.) Which buffer should I be using and do they make heavier or lighter rifle length buffers?
March 29, 2022
They make both heavier and lighter rifle lengths the better one depends on your preference.Using a heavier one will help with felt recoil but putting one that is too heavy may hinder cycling. A lighter one will allow for more felt recoil and will likely cause the upper to continually hammer itself.
I just purchased a barrel
March 26, 2022
I just got one of your 16 inch 12.7x42 barrels and was wondering what needs to be done to a standard 7.62x39 bolt with the .125 spacing in order for it to work my jams on loading as will as smashing bullet into the cash suggestions?
March 29, 2022
We recommend all modifications be done by a competent gunsmith. Please consult with a gunsmith on the best way to make any modifications. We will recommend that you get the correct bolt to use depending on the caliber.
June 4, 2022
what about using a hydraulic buffer with a beowuff?
June 6, 2022
We do not use or recommend hydraulic buffers here at BCA.
Ronald Perdue
June 26, 2022
Great article.
Russell Suender
November 5, 2022
It'll br my next upper.My choice woul# be the 50 Beo with dust cover and forward assist with the 18"barrel.
Bob in La.
April 11, 2023
That big half inch hole in the barrel cuts a lot of weight in a fat barrel. A Magpul MOE or CTR stock with a Limbsaver pad added keeps the recoil comfortable and still minimal weight for a hunting gun. A current production Thermold 20 rd mag is light. holds 5 rds, and doesn't rattle like a metal one, and the feed lips seem to be thicker than most other poly mags. No problem with rounds popping out. And it's cheap, 100% function in my experience. If you think you might be over run by hogs get the 30 rd which will hold at least 10 rds.
Anthony Pickett
May 27, 2023
Great article! Really enjoyed it. Very Informative.
August 9, 2023
Just an FYI, the 350 legend mags from Wilson Combat work well for the Beowulf and work Ok for the 450 bushmaster as well. I reload the 465Gn powder coated lead bullet with 27Gn of Lil Gun and can make golf ball size hole at 100 yards, this thing is blast to shoot, Get the heaviest buffer and spring you can find, enjoy the bliss!!!! OH, and stick with the the starline brass, they dont split.
Leon w Chapman
September 19, 2023
Still waiting for the 18" upper to come back in stock. Worst it has dropped off my wish list, and notify me when available.
mark tulak
December 3, 2023
when will the muzzle break be available they have been out of stock since I purchased my upper
Lloyd Smale
December 5, 2023
waiting patiently for beo pistol uppers to come back
Francisco Zorrilla
December 9, 2023
When you start to make a left eject rear charging?
Thomas Townsend
May 13, 2024
Which spring do you recommend with the H2 or H3 weight?
Daniel Gorbea
May 13, 2024
I have three of your 12.7x42's, one is 10.5 inch pistol, one is a carbine gassed 16inch, and one a mid gassed 18inch. The shorty (right charging) is still getting the lower built for a pistol, so I use the BCG from it in the 16 inch rifle, with a BCA blem big bore right side charging upper receiver I got for $40 from y'all and a beautiful stainless heavy barrel. Its mounted on a Diamondback lower. Its real pretty. Both the 16 inch and 18 inch are buffered with the Armaspec SRS Stealth Recoil Spring system for big bore rifles. I got a deal on the buffers for $64 a piece thru Midway. The Armaspec runs for about $95 to $100 on their website, so I jumped on the deal. Best decision I ever made. Saves my shoulder from all that punishment and makes the firearm fun to shoot!
Daniel Gorbea
May 14, 2024
When is Bear Creek Arsenal going to make a Boron BCG for the 12.7x42? Just asking?
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