AR 15 Conversion Kits – Best 5 Types You Should Own

By Thomas Conroy
AR 15 Conversion Kits Top Five Product Review

AR 15 Conversion Kits
AR 15 Conversion Kits – Best 5 You Should Own
AmmoLand Gun News
AmmoLand Gun News

USA –-(Ammoland.com)- AR-15s are modular, hence the AR 15 Conversion Kits.

Push out the takedown and pivot pins and remove the upper – it contains the barrel and the matching bolt carrier group, the charging handle and the gas system.

If you’ve zeroed an optic or scope, it comes with the upper, too. Replace the original upper assembly with a different one; push the two pins back into place, and voila! You’ve got a different gun.

Standard 5.56mm lowers can’t accept larger .308 uppers, and vice versa. But there are plenty of AR 15 Conversion Kits in all sorts of calibers that will work perfectly with standard 5.56 lowers, and the lineup seems to expand all the time. There are many complete upper assemblies available that are literally “plug and play” on any standard AR lower assembly.

And if you’re comfortable with a few basic tools – like a vise and a barrel nut wrench – you can easily build up your own stable of extra AR-15 complete upper assemblies. Quality suppliers like Brownells have all the barrels, uppers, handguards, bolt carrier groups and associated tools you’d need.

Why would anyone go to the trouble of getting a bunch of uppers to go on just one AR-15 lower?

Magpul BAD Lever
Magpul BAD Lever : http://goo.gl/TzoCGT

Think of it this way. You’ve spent time and money getting the exactly the trigger you want, and the best stock that fits you perfectly. Maybe you’ve added a Magpul BAD Lever, and the ideal pistol grip for your hand. Why should you give all that up just because you want to do a different kind of shooting, at a different distance?

The good news is that you don’t have to, at least not if you get a spare complete upper assembly or three. That way, you can use the same gun for everything from plinking soda cans on the family farm, to sniping steel targets way out there, to hammering feral hogs in thick brush, just by pushing two pins and swapping uppers.

I’ve put together a list of complete AR 15 Conversion Kits assemblies every Black Rifle owner should consider. I’m basing this list on the assumption that you’ve already got an AR-15, most likely a 16-inch carbine in 5.56. And if you don’t yet, now is the time to buy, as there are tons of bargains out there on 16-inch carbine style ARs in 5.56.

But here’s my list of the Top 5 AR-15 Uppers every Black Rifle shooter should think about owning.

5) A Big Bore AR 15 Conversion Kits :

458 SOCOM Ar-15 Upper
458 SOCOM AR 15 Conversion Kits

As good as the 5.56 cartridge is, there are some things it just doesn’t do that well. Delivering whomper-stomper hits on big, tough game animals like feral hogs is one of those things. There are several different big bore cartridges out there designed to fit through an AR-15 magwell, and it seems like more are developed by creative wildcatters every year.

Some of the really popular big bore AR cartridges include .450 Bushmaster, .458 SOCOM and .50 Beowulf. All of them throw big fat bullets at relatively slow velocities, and are devastating at close range. If you want readily-available factory ammo, .450 Bushmaster ( http://goo.gl/Ish1pq ) might be the best bet. If you handload, .458 SOCOM probably gives you the most versatility, as it uses rifle bullets available in a wide range of weights and styles – as heavy as 600 grains if you want.

And if you really must have a caliber that starts with a 5, and is named after an epic hero, then .50 Beowulf is the only choice.

Cross Machine Tool Co - AR-15 458 SOCOM Billet Upper Receiver
Cross Machine Tool Co – AR-15 458 SOCOM Billet Upper Receiver : http://goo.gl/ft1rjF

Perhaps the best aspect of adding a Big Bore AR 15 Conversion Kits is that you can typically use standard 5.56 magazines, although Bushmaster does add a special “single stack” follower and springs to standard 20-rd magazines specifically for use with .450 Bushmaster ammo. Any of these cartridges will give your AR-15 performance similar to the venerated 45-70 at close range, in a lightweight, semi-auto package. The possibilities are endless.

If you decide to build your own Big Bore AR 15 Conversion Kits assembly, be sure to either enlarge the ejection port, or get an upper ( http://goo.gl/ft1rjF ) with an ejection port specially made to accommodate the big fat cartridge cases.

4) A 6.5 Grendel AR 15 Conversion Kits :

6.5 Grendel Ammunition
6.5 Grendel Ammunition : 6.5mm Grendel round showing variety of bullets 144 gr (9.3 g) to 90 gr (5.8 g)

The 6.5 Grendel ( http://goo.gl/ec9d7h ) is an amazing cartridge. It uses 6.5mm bullets, known for having good sectional density and relatively high ballistic coefficients – which means they fly very well, even in stiff crosswinds. The Grendel gives performance similar to, if not better in some ways as the .308, but in a cartridge that can fit inside a standard AR-15 lower.

C-Products AR-15 6.5 Grendel Magazines
C-Products AR-15 6.5 Grendel Magazines : http://goo.gl/MWoygi

Just a few years ago the 6.5 Grendel’s creator, Bill Alexander, opened the door for even more manufacturers to crank out ammo, parts and barrels with the name “Grendel” on them.

Not surprisingly, Alexander also first developed the .50 Beowulf, and took the Grendel’s name from the same Old English saga.

Unlike the Big Bore uppers, a 6.5 Grendel will require a magazine specially shaped for that round. For reaching way out there with a standard-sized AR-15, it’s hard to beat the 6.5 Grendel.

Be sure to add a good-quality scope and some nice rings to complete the package.

3) 300 AAC Blackout AR 15 Conversion Kits :

300 aac blackout vs 223
300 aac blackout vs 223

The 300 AAC Blackout cartridge gives performance very similar to the 7.62×39, but in a cartridge that works perfectly with standard AR-15 bolts, magazines and lowers. You can convert any standard 5.56 AR-15 to .300 AAC Blackout by merely changing only the barrel. Of course, if you don’t want to mess with taking apart your current upper, you can just drop a complete 300 AAC Blackout AR 15 Conversion Kits onto your lower.

Why not go with an AR-15 upper in 7.62×39 in the first place? You can use less-expensive steel-cased ammo in a 7.62×39, but there are tradeoffs. Typically, you’ll also need to put in an extra-power hammer spring to help reliably ignite the sometimes-harder primers found on cheap, foreign-made steel cased ammo. Many shooters also add in special firing pins to help set off primers in less-expensive steel cased ammo.

Finally, you must have specially-shaped mags for a 7.62×39 AR. But the 300 AAC Blackout uses the standard 5.56 mags that you probably already have in good supply.

Advanced Armament - AR-15 Upper Receivers in 300 Blackout
Advanced Armament – AR 15 Conversion Kits Receivers in 300 Blackout : http://goo.gl/o20pF8

Where the 300 AAC Blackout really shines is with sub-sonic loads combined with a suppressor. Suppressed, it is remarkably quiet, has little recoil, but still lets you thump targets with bullets that weigh up to 220 grains. If you live in a state that allows suppressor ownership (congratulations, Minnesota!), you really should consider getting an upper ( http://goo.gl/o20pF8 ) in .300 AAC Blackout with a suppressor-ready muzzle device.

2) 22 LR AR 15 Conversion Kits :

Yes, I know we’re still in a .22 LR drought, but there seem to be signs of it easing. Maybe. Even with .22 LR hard to come by in some locales, a dedicated .22 LR upper makes a lot of sense for AR-15 owners.

You can get conversion kits ( http://goo.gl/15lav6 ) that let you shoot .22 LR through any standard 5.56 AR-15, just by swapping out the bolt and carrier group and using a special magazine. And these kits are almost always less-expensive compared to dedicated .22 LR AR 15 Conversion Kits. Many shooters get these kits, and enjoy them a lot. But there are some reasons why you might want to consider a dedicated .22 LR upper.

First, dedicated .22 LR uppers  ( http://goo.gl/Dh7k0g ) typically have barrels specifically rifled to work with slower, lighter, all-lead projectiles fired from rimfire cartridges – something like a 1-16 twist. The twist rate in your 5.56 AR-15’s barrel is intended for 55 grain, or heavier, jacketed bullets moving at much faster speeds. The slower twist rate often results in better accuracy from a dedicated .22 LR upper compared to a conversion kit.

Tactical Solutions - AR-15 .22LR M4 Upper Receivers
Tactical Solutions – AR-15 .22LR M4 AR 15 Conversion Kits : http://goo.gl/Dh7k0g

Second, true .22 LR uppers are blowback, and don’t need a gas block or gas tube, and are thus often lighter. Your 5.56 AR still wears its gas block and gas system parts when you swap out just a bolt carrier group and magazine to convert to .22 LR.

More accurate and lighter easily translate into more fun, which are both important, especially if you’re using your .22 LR upper to help introduce young or new shooters to the game.

1) A Varmint or Precision AR-15 Upper in .223/5.56

Mk 12 Special Purpose Rifle
Mk 12 Special Purpose Rifle

Let’s say you have a 16-inch AR carbine, and you’ve carefully selected the stock, trigger and pistol grip that suit you best. You aren’t interested in having to worry about another caliber, but would like to be able to reach out a little farther and a little more precisely.

Your best bet might be to invest in a dedicated varmint or precision AR 15 Conversion Kits, especially one with a high-quality scope mounted.

Here’s how that combination could work. The 16-inch carbine upper is lightweight and fast handling, especially if you put a red dot or similar electronic sight atop it. With that rig, you can get quick hits inside of 300-yards, exactly what you need for self-defense, many types of action shooting sports and certain types of hunting.

But what if you could convert the same gun into a tack driver in less than 60 seconds, and then smack small targets and varmints, out to 500 yards, or maybe even farther?

If you’ve got an upper with a free-float handguard, bipod, long-range scope and a heavy target barrel ( http://goo.gl/LROOJE ) – especially one with twist rates optimized for match-grade ammo tipped with bullets up to 77 grains ( http://goo.gl/CztYRc ) , you can – provided you develop your shooting skills enough.

DPMS AR-15 TAC2 Upper Receiver Assembly
DPMS AR-15 TAC2 Upper Receiver Assembly : http://goo.gl/LROOJE

It’s an idea that even the US military likes, with the various versions of the “DMR,” or Mk 12 Special Purpose Rifle sharing several of those features. Of course, just slapping a free-float, heavy-barrel AR 15 Conversion Kits onto your carbine lower will not magically transform it into a Mk 12 SPR, but it can give you some real upgrades when it comes to longer-range performance.

New Take On Old Saw

There’s an old cliché out there that goes something like this, “Beware the man with only one gun. He probably knows how to use it.”

But if that “one gun” is an AR-15, it can quickly turn into a whole lot of different guns, just by pushing out two little pins, slapping on a new AR 15 Conversion Kits assembly, and pushing those two little pins back into place.

 

Thomas Conroy is a firearms aficionado and writer who lives in the Midwest.

  • 55 thoughts on “AR 15 Conversion Kits – Best 5 Types You Should Own

    1. With the popularity of 9mm uppers, mag-well pugs for S&W mags and deicated lowers for Glock mags I can’t beleive you did not even mention 9mm?

      1. agree… I know it’s a little late to comment on this year+ old post… but 9mm is actually what I came to this article to find out about…

        1. Haha. I still answer questions beat I can from this article all the time. I wouldn’t worry about how old it is. It’s a good article.

      1. I mention this as an old Thompson shooter…we got a lot more velocity from the .45 ACP than from the five inch 1911 barrels. This would make me a great farm gun for pests and….whatever.

        A wringing out of such a piece, with the writer shooting at fifty yards, minimum, would be outstanding. Far more practical, for my farm, than the .223…

        1. .45 ACP and subsonic .300 AAC have nearly identical specs if you compare them, with the .300 giving you better coefficient and a lot more power in the supersonic range as well.

          .45 ACP – 230 gr with a muzzle velocity ~830-1050fps
          sub .300BLK – 180-220 gr with muzzle velocity ~950-1050fps
          super .300AAC ~2000-2300+fps

    2. Can i just buy a complete 300 blackout upper and install it on a 5.56 complete lower and have a working AR 15? I’m looking in to getting my first AR. Thinking of buying separate pieces and then just put them together. Thank you

    3. I’m curious now. Would it be possible to have an upper fit for .22×.250? That would be the ultimate varmint rifle.

      1. Don’t plan on it. Nemo has an AR in 300 win Mag. It’s completely proprietary, so it’d be the same style of design. If you want one, you’re looking 7k if it comes to production. Even more now considering it’d be a completely custom rifle. And there’s a much better caliber. See if you can find some info on the 260 Dingo. A company in my town makes the bolt guns for it. Just shy of 4k fps. They’re getting jackets to shred past 3975fps. They’ve shot coyotes at 425 that took lungs out the other side, and one at 600 that you could fit your fist inside the neck where it removed vertebrae. 8″ of drop at 700 yards, trying to get them to ORSA so they can see her perform at a grand. So far, best $1600 I ever spent on a gun.

          1. I do believe Falcor and Nemo are the only two making them I very well might be wrong but I have seen the Nemo in person but have only heard of Falcor making one I also seen a Nemo in 338 Lapua the last time I went to my local shop and almost died when I seen the price tag

    4. i have a bushmaster 5.56/223 you are saying that if i buy 300 blackout kit that it will switch out with no need to buy anything else??

      1. All you need is the 300 blk out upper for your bushmaster. Mags are interchangeable since 300 blkout uses the 5.56/.223 casing. I’d encourage you to steup a trust and get a SBR and the 9″ barrel like I did.

        Buffer & tube springs you’ll want jp or spikes. For extra tweaking.

    5. What would it take to convert supper .17 to ar platform i would like to do just that small fast round low coast ammo .or am i just dumb .?

    6. Hi, Kinda new to this. I have a .22 Mosberg would like to know if I’m able to upgrade to a bigger caliber and what parts I would need.
      Thanks for any input

      1. No you can not. If you had something along the lines of the Smith & Wesson M&P15-22, yes. However, that’s not what you have. You have a designed “AR” in 22LR. Good gun, keep it fed. But if you want something you can convert, have to get the real deal.

      1. There is a new feature of the internet that allows you to search for such things by simply entering the words you want to search for into a little box and hitting the enter key. Give it a whirl. It’s http://www.google.com. You’re welcome.

    7. Stupid question on my part. I have a colt at-15 in .223. Can I just swap out a 5.56 barrel to shoot 5.56 or is there some other changes I need to make?

      1. Be careful. Some 5.56 ammo fires at higher pressure than the .223 your Colt was designed for. Double and then triple check that your Colt upper can handle 5.56 pressure.

        Or get a complete 5.56 upper.

      2. If your Ar15 is original Colt product, check the barrel behind the muzzle and front sight. It will be marked with the cal. the barrel is rated for, the rate of twist, and barrel contour/weight. I own 8 original Colt AR’s and they all have these markings.

    8. so as i have read my i have a multi caliber smith and wesson OR edition, so if i read everything correctly all i need to do is get and upper for 300 blackout and im all set..

      1. All you need is a 300 blackout barrel. But yes. If you go ahead and make it easy on yourself and just buy a complete 300 blk upper already put together then yes. You’ll immediately be shooting 300 blk. But be VERY VERY CAREFUL not to accidentally try and shoot a 223/556 in your blackout upper. That could be very very bad. I suggest only taking either the 300 or the 223 out at a time. Never take both to the range. And I would even mark your magazines somehow as not to accidentally mix them up. I personally use only metal magazines for my 223/556 and polymer for my 300 blk

        1. You have it backwards ALLEN. What you never want to do is shoot a .330 BLK in a .556/.223 because certain .300 BLK rounds will chamber in .556 rifle. It may fire…once but a .300 BLK bullet will absolutely not go through a .556 barrel without catastrophic failure. 556 will not chamber in .300 BLK barrel because .556 is a much longer round.

          1. A instructor in in San Diego had a student that had very bad day last summer due to his inattentiveness And neglect. He was teaching a student who put a mag of 110gr .300 blackout in a .556. the rifle fired blowing the upper and the guys right forearm all to hell. The student was a lefty and he cought most of the blast mid right lower arm. How the instructor missed it remains unknown but he must have been paying attention to something else. Why he had two different calibers rifles out in the first place is also unknown as is why mags with the different rounds where also out at the same time. I guess details will come out in the law suit that the student filed against the instructor. The range is not being implicated in the lawsuit fortunately. Also of note the instructor was not related to the gun club in anyway he was a private instructor and not a very good one at that obviously
            I use only Hex mags for my r300 blackout rigs giving me tactile feel instantly telling me what caliber is in the mag. For my 5.56 I use standard GI or PMags. In this way I can tell just by feel what kind of ammunition is in the magazine. I also never have a mixture of the two hours at the same time

          2. I may have it backwards sir. My point was to BE CAREFUL. Do not take 300blk and 223 out at the same time. There is no need to. It just makes sense to keep your range time to one predetermined caliber for obvious reasons. But. Thank you staff sargeant for setting me straight.

    9. That was a good article. I didn’t know that with some different chamberings magazine mods would be necessary. And why do only half of my replies show up because I am not rude or hate on people or even cuss like some of the folks on here do I’m just wondering

    10. It should be mentioned that a .300 Blackout round will chamber in a .556 upper, with disastrous consequences! Be careful!!!!

    11. All of my 5.56 AR rifles & mags are black. All of my NON-.556 AR guns & matching magas are a different color, like Cerakote Burnt Bronze, or Magpul FDE. That way I don’t end up trying to load a 458 SOCOM round in a 6.5 Grendel riffle, etc.,

      1. Use a Cold hammer forged FNH doudle chrome lined barrel. Its also refered to as their Machine gun steel barrel. It is the same barrel found on the military issued rifle it just has the FNH logo instead of the manufacture number stamped on the barrel. You can pick up the barrel or the complete upper at Palmento State Armory about the cheepest anywhere if you are willing to wait. This barrel will provide the best life you will find in my experience. watch the temp of the rifle doing mag dumps or you will blow your gas tube out. It is designed to blow out before the barrel so pay attention and do not be stupid about not letting the rifle cool between mags! I do not advise 100 rd mags for a bumpfire stock as you will burn up the barrel and the action quicker than you think. It might be fun but it is also detrimental to the weapon in every way. Stick to 30-40max mags and only once in a while if you do not want to replace parts all the time. A bump fire stock is all and good but learn the weapon and its capabilities and you will have a lot more fun and enjoyment with it. Full auto fire has been proven to be very ineffective with the exception of laying down supperssing fire and there is very little need for that unless on a battlefield and even then aimed shots are much more effective 99.9% of the time. There is a reason that full auto is refered to as a fun button/switch. Be careful untill you know how the weapon is going to react and how you are going to react. There is a learning curve. Start with no more than 3 rounds to begin with and increase the roung count only after becoming extreamly familiar with the way the weapon reacts. learn how to fire single fire and than two and three round bursts and progress from there always being in control and being safe at all times. You asked and I threw in my 2 cents.

        1. Haha, yeah this was an interesting reply from Mr. Walker. I was just going to say get the cheapest chromelined one you can find (or several of them) and go have fun. I imagine you’re not Shooting for accuracy with a bump fire stock and all, so as long as you don’t over heat it to where it warps or has other permanent danger issues, then keep on keeping on. But I’d say follow his 2 cents rather than mine…

          1. The little cartoon book the Army called a field manual that was issued with the A1’s stressed under sustained fire no more than 15 rounds per minute to prevent damage to the barrel.
            That is not a “rock and roll” number.

            1. The army also wanted each barrel to see a minimum round count of 25 to 30 thousand rounds per barrel/weapon. This was proven it to be unrealistic so was their 15 rounds per minute. The stated manual was written by bean counters that only had a cursory knowledge of the rifle that had experienced major issues in early life due to the development of the 5.56×45 cartridge over the .223 the rifle was initially developed fire. Hence major improvements and than the A2. 15 rounds per minute will not damage a barrel. 60 rounds in a minute will not damage or hurt a barrel if let cool properly after firing. It will help to burn out a barrel faster however. The barrel is not the weak link in the AR it is the gas tube. If pushed to high a high temp due to high rates of fire the gas tube will blow before the barrel is pushed to dangerous limits. It does not mean that the barrel is not suffering premature wear and erosion of the throat or the gas port. The chrome lining can also be effected with high rates of fire. The USMC and Army now states that a M16-A2 or M4 can fire up to 45 to 60 rounds per minute of use in short engagements letting the rifle cool as much a possible and rapidly firing of no more than 5 consecutive magazines should be avoided with out cooling unless being overrun in order to keep temperatures down and avoid burning off lubrication and seizing the weapon up. They also recommend cleaning and lubricating the weapon every 250 to 400 rounds whenever possible and after every patrol or firing when returning to base. The AR-M16 platform is a pretty robust weapon system but one that needs maintaining, likes to run wet and will take abuse but when abused will need a much higher maintenance schedule including the replacement of parts as they wear.

    12. No mention of the 450 Bushmaster, probably more popular than any of the conversions mentioned. Also, some of the suggested conversions wouldn’t allowed to work due to magazine / mag well incompatibty issues related to using a ,223 / 5.56 lower.

    13. Thanks again Mr. Walker for the info the reason I was even considering a bump stock because I ran across it in a you tube video and it looked like a lot of fun, Mr. M I was shooting for accuracy but seen this bumpfire and looked like some fun once in a while since our government don’t allow auto fire guns without a permit and my CPL don’t count (sad) but with that said a chrome lined barrel wouldn’t be a bad idea any suggestions for a M&P -15 smith and Wesson gun I picked up about 5 yrs. ago at gander mountain here in Michigan?? thanks again

      1. I think I would still find a 16 or 18 inch FNH cold hammer forged double chrome lined barrel. Their accuracy is very good my 16 inch and 20 inch barrels both shoe well under 2 and a half inches with iron sites consistently at 100 yard. Scoped I’m averaging well below – it depends on the day best groups are about .42 with the 20 inch and about .53 with the 16. I think when you comes to a grill them lined barrel the FNH barrels are hard to beatand give maximum life. If you’re looking for true accuracy Noviski is the foremost leader period. FMH barrels depending on where you buy an average about 250 to 350 for the barrel. If you go to Palmetto State Armory and you’re willing to wait you can get a complete upper for 350 minus the bolt carrier group

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