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Ammo prices are down from the shortage prices a few years ago. That doesn’t mean that they’re cheap, but some ammo is definitely more affordable than others. 9mm is about as cheap as you can get in centerfire ammunition, and it might make you wish you’d picked up a 9mm AR.
If you have a rifle caliber AR-15 and want to drop a 9mm upper on it, you can always get a mag well adapter that uses pistol mags or Colt SMG mags. The adapters run anywhere from around $70 to a couple hundred bucks and then you still need mags, unless you already have some on hand. There’s also the issues of reliability with a conversion and ease of swapping your gun back to its original caliber when you want to. If you want to bypass all of that, an easier solution is to use the ExoMag from MEAN Arms.
But First, the EndoMag
MEAN Arms isn’t new to the 9mm conversion mag game. They’ve been making EndoMag conversions for a while now. The EndoMag is a drop-in conversion kit for Magpul Gen 2 or later PMAG’s that let you use 9mm in your existing magazine. Simply disassemble the magazine, pull the spring and follower and replace it with the MEAN unit. The EndoMag comes blocked to 10 rounds, but you can cut the “plug” to allow it to hold 20, or 30 rounds if your state allows it. Converting your existing mags is as fast as swapping out the spring and follower.
Make sure you do use Gen 2 or later mags though. Initially I dropped the conversion in a Gen 1 mag and had feed issues. When I swapped out to a Gen 2 mag the issues went away.
The EndoMag conversion has an ejector built into the mag, which is important for a 9mm conversion. Most dedicated 9mm AR’s have the ejector located in the lower. Since you’re using these mags in a rifle caliber lower, that ejector isn’t present, but MEAN puts it right on the magazine. Endomag conversion kits cost $29.99 and you need donor Magpul mags to work with.
Enter the ExoMag
If you like the idea of the EndoMag, but would rather have a dedicated magazine, then the ExoMag is what you’re looking for. These mags are made from scratch as 9mm mags. They still fit a regular rifle mag well, and are the same dimensions as an AR mag. That means that you can still use AR rifle mag pouches and carriers.
One thing I like with the ExoMag is that it is visually different from a rifle caliber magazine. Since the 9mm is much shorter than a 5.56 it only takes up a portion of the magazine width. MEAN skeletonizes the rest of the mag. This lets you know at a glance that you have a 9mm mag. On the EndoMag conversions I wrapped mine with tape so I could tell quickly which were converted to 9mm. You don’t need to do that with the Exo’s.
The first Exomag release is the big 40 rounder, and that’s what I had on hand to test. There will be 32, 20, 15 and 10 round mags available later. I’ll be honest, I’d have rather MEAN started with a smaller mag, as the 40s are pretty long. And honestly. I was a little skeptical on the reliability as problems seem much more common with the higher than normal capacity mags. But I was definitely willing to give them a run through. Exomags are priced at $35 for the 40-round mag and progressively dropping in price all the way down to just $20 for the 10 round mag.
Test Platforms
I used three different guns to test both the Endo and Exo mags. All three started out as 5.56mm SBR’s. On one I pulled the upper from my H&R 635 clone. The next I used the Bearing Delay Upper from MEAN Arms. This one used a slightly different version of the ExoMag since it has an ejector built in to the bolt. This negates they need for one on the magazine like the other conversions.
For the last one I used my Spikes Tactical 9mm upper. For the haters in the peanut gallery, yep my Spikes is still rocking a Keymod handguard. It’s an older gun and it works, so I don’t mess with it. I think I still have three older SBR’s with Keymod.
Anyway, aside from swapping the uppers, I needed to use the heavier buffers from the 9mm PCC’s as well. Being a blowback system the 9mm AR’s need a heavier buffer to cycle, so you have to swap out your rifle buffer when you move to 9mm. Unless you use the MEAN Arms Bearing Delay upper. MEAN designed that one to be a one for one swap without needing to swap buffers since it isn’t a blowback system.
Range Time
With converted guns in hand, I headed to the range. As a matter of fact I hit the range with the test guns a number of times over the summer. The MEAN Endo and Exo mags engage the bolt hold open of your AR lower so operation is exactly the same as your rifle caliber AR. Being that the mags are the same dimensions as a rifle mag, reloads feel the same as well, which is nice for continuity of training.
In addition to my two uppers, I also used two uppers from a buddy of mine as well. He has a Foxtrot Mike FM-9 carbine and a home-built SBR. With my lowers and the five uppers I ran at least three hundred rounds through my set of 3 EndoMags and three Exomags. Reliability was 100% on each range session.
We had a good mix of ammunition as well. From crusty surplus ammo to modern defense ammo, and both FMJ and hollowpoint loads. Bullet weights ran from 115 up to 147 grains. The MEAN mags presented and fed everything with no issues whatsoever. Despite my concerns about the 40-round mags and reliability, that didn’t prove to be an issue either. I think my skepticism of mags over 30 rounds comes from 5.56 AR mags, and I generally stock to 10-, 20- or 30-round mags. Although I do have a few Magpul 40-round mags and they do run, even though I rarely use them.
Durability seems as good as any mag. I let the Exomags drop to the concrete or gravel, depending on where I was shooting, when I reloaded. No issues presented themselves. They also rattled around around in my ammo cans and remained loaded between range sessions.
The ExoMag Advantage
Swapping to 9mm is easy with the ExoMag. You can use your existing lower with no modifications other than swapping out the buffer tube. You don’t need to deal with an adapter that adds expense and complexity to your rifle. Training is simplified since you’re using the same profile mags, and same operating principles as your AR in its original rifle caliber.
If you have a surplus of PMAG’s then the EndoMag conversion may be a good option for you. But if you’re buying from scratch, I’d give the nod to the ExoMag. It’s a dedicated 9mm platform that you can tell at a glance is made for 9mm. It’s also cheaper to buy the ExoMag than it is to buy a PMAG and a conversion kit. You can order the 40-round ExoMags right now and put in a pre-order for the lower capacity versions. I plan on grabbing some lower profile 20-round magazines when they’re available. If you’ve been thinking about adding a 9mm upper to your existing AR and had hesitated not knowing what mag system to use, then definitely check out the ExoMag from MEAN Arms. It’s an easy and reliable solution to your problem.
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I’ve had a 9mm conversion project in the back of my mind for awhile now. These new mags may move it forward a couple notches. This is a great country.
hawkeye,
I have also been thinking about a 9mm conversion. My research up to this point is absolutely zero: thus I had no idea that I would need a different buffer tube and some method of empty casing extraction. (I was hoping that I could simply remove a 5.56mm upper and install a 9mm upper.)
I have to research what is necessary and reconsider. If I decide to convert a 5.56mm to 9mm, I will almost certainly be buying one or more of these EndoMags or ExoMags.
(Note: I do not want to create a dedicated AR-15 chambered in 9mm Luger–I want the ability to quickly and easily convert one chambered in 5.56mm NATO to 9mm Luger and back again, assuming that is even possible.)
Search: Bufferless 9mm upper
Example result: https://matadorarms.com/product/mat-9-9mm-ar-upper/
Can’t speak on the barrel length or other legalities based on the upper/lower combination but it is 100% possible for one to convert from 5.56mm to 9mm by just swapping the upper & magazines with no buffer-weight & spring swap needed.
I’ve seen a couple ways to do this, as noted in the article above and posts below. I haven’t decided which yet, thus still on the back burner.
I began with a S&W M&P2 that I got on sale several years ago. I bought it to play with and learn the platform. I got one of the CMMG 22LR conversion kits for Christmas. Super easy mod, just swap out the bolt carrier group and load up one of the .22LR mags, and you’re ready to burn powder. Wish they also made one for 22 magnum. Because I have that in the gun (great backyard pest medicine), I don’t really NEED the 9mm conversion kit for cost of ammo savings so it isn’t a priority. One of these days my attention will turn back to it.
Those are neat for training and the likes. I actually run a Promag block of all things and it’s not problematic. I use ASC mags in it.
Question for the Armed Intelligencia:
What is necessary to convert a “standard” AR-15 chambered in 5.56mm NATO to 9mm Luger? I was thinking (apparently incorrectly) that I could simply purchase an AR-15 upper chambered in 9mm Luger and just swap out uppers. This article tells me that I would also need a different buffer tube and a special magazine with an ejector. What is the “ejector”? Is that for ejecting the magazine or extracting empty casings out of the chamber?
The article is incorrect, you need a heavy buffer but not a new buffer tube.
5.56 carriers have an ejector, 9mm bolts do not. Both have an extractor, but once the brass is out of the chamber you need to pus it out the ejection port. Glock and Colt mag conversion blocks have a fixed ejector, so the bolts don’t need one. Endo mags need one since they don’t have the conversion block.
So to convert a 5.56 rifle to 9mm you will need a 9mm upper, a heavy buffer, and either a mag conversion block with ejector or one of these Mean Arms mags with it’s own ejector.
How to convert 5.56mm AR to 9mm AR in two steps:
1) Bufferless 9mm upper designed to fit standard AR lower. Quick web search will return examples.
2) MEAN Arms mags/conversions.
No buffer weight change necessary.
SteamTroller45 and No_Ones_Home,
Thank you for your helpful responses. The commenter “sound awake” below has convinced me that I am probably better off using the money that I would spend on a 9mm Luger conversion to simply purchase more 5.56mm NATO ammunition or even a dedicated 9mm Luger carbine.
10mm. EOM.
exactly
a pcc isnt ever worth doing
unless its in 10mm
and has a 10.5 inch max barrel length
XZX,
To be sure, a short barreled rifle (plus a suppressor) chambered in 10mm Auto and loaded with hot/potent ammunition would be an outstanding close-quarters combat platform. I just wish that local gun stores had a decent selection of 10mm Auto ammunition at prices anywhere even somewhat close to 9mm Luger cost.
Then we have to ask whether it makes more sense to just buy an AR-15 upper chambered in .300 AAC Blackout.
Decisions, decisions, decisions. Isn’t choice a grand thing?
ok so just to be clear:
by the time i buy enough exomags
to occupy the mag pouches on my rig
a 9mm upper worth buying
a 9mm buffer
some sights worth buying
an optic worth buying
and run a bunch of ammo through it
to sight it all in and make sure it works
i will have spent over $700
“just to save some money on ammo”
without a doubt i would rather just buy another couple thousand rounds of ammo for my other ar15s chambered in 5.56 7.62×39 and 300 blk
sound awake,
Excellent commentary and financial analysis. (You made me chuckle out loud.)
I was thinking of a 9mm Luger conversion to save money on ammunition–and you just convinced me that I would probably be better off just using that money to buy more 5.56mm NATO ammunition.
At this point, the only reason that I can see to acquire an AR-15 conversion is if I want (intentionally) reduced power/blast from 9mm Luger over 5.56mm NATO while maintaining commonality of controls/operation with the AR platform. And with that $700 price tag (which does not include the cost of the AR-15 lower, stock, trigger) I might as well just purchase a dedicated 9mm Luger carbine which will often cost less.
Lots of questions about AR9s here. Let me throw a few pointers out that I’ve picked up over time.
-First off, the buffer tube is the same for an AR9 and a conventional DI/piston AR.
-The buffer is typically swapped. If you operate a blowback AR9 with a standard buffer you will almost certainly see over velocity and probably over travel. I broke a mag catch before realizing this in the day. Also the recoil impulse isn’t great.
-Buffer weight is your tuning. If you don’t have a heavy buffer (I run an 8oz one) you can shove about $2 in quarters into the buffer. I ran one quite a while this way.
Bolts:
-There are potentially 4 bolts that an AR9 can have. These are:
Ramped/Single stack Mag
Ramped/Double stack mag
Unramped/Single stack Mag
Unramped/Double stack mag
Single vs double stack is common sense. The part that engages with the mag in a double stack setup is wider.
Where things get weird is ramped vs unramped. If you look at the bottom of the bolt, it will well have a ramp from the face to about the half way point of the bolt. An unramped bolt will just be flat on the bottom. If you have a ramped bolt you don’t need to have a notch in the hammer. The unramped bolt requires a hammer notch.
-Receivers and mag blocks:
There’s a lot of choices here. Purpose built receivers exist for a lot of mags, as do blocks and mags like the Endo and Exo mags.
“Colt Mag” style blocks use modified Uzi magazines in effect. A lot of stuff did this. They use a stock style mag catch and bolt hold open as well. If you use ASC style mags they have last round hold open. Uzi mags will not.
There’s a few different makers of blocks, and they fall into two categories. “Top feed” vs “bottom feed.” Once again, common sense comes into play here. The top feed blocks I’ve used (Promag) have the disadvantage that you have to pull the bolt catch to put them in. I drilled and tapped a hole for a set screw in my lower and cut the tabs off so I could put it in from the bottom. For you guys with a 5.56 lower you’ll want to have a bottom feed block to go back and forth easily if you go the block route. These blocks will have the ejector built into them. As a warning about the Promag blocks, I found that the loose ejector means you’ll want to have your AR ejection port down as you close the upper and put in the take down pin. Otherwise you’ll have issues pulling the bolt the first time. It’ll be fine after just annoying the first time. I run Steel ASC mags in the Colt style personally, NEVER had an issue I’d attribute to the mag with them. They’re fantastic although heavy.
Purpose built receivers are self explanatory. The most obvious choice is Glock Mags but others exist. There’s even some 3D print stuff out there too. Someone make me something in an S&W Sigma/SD9 please. 🙂 There’s tons of choices here from billet to polymer to forged. Like the mag blocks these will have an ejector built into them.
The Endo/Exomags are pretty well covered in this article. I’d to end up with Exomags just because of the economics of it, and not wanting to waste perfectly good pmags for it.
Something cosmetic that you can do is they make a deflector for 9mm that has a half length door on it. It fits into a standard ejection port. I think they even make short port uppers now that are for 9mm as well. You can run a standard length ejection port and door as well with no real impact.
-There’s lots of barrels out there. Not much use going above 12″ if you’re not worried about legality. Profile can be whatever you want it to be. If you don’t need a front sight you absolutely can skip the gas block too. May as well shed a few ounces.
That’s all you really need to know. really. If you want the TL:DR version, here’s how I’d build an AR9 using Endo/Exomags if it were me:
-You need a heavy buffer or quarters. STOCK BUFFER TUBE.
-You want to use a ramped bolt so you can use a standard, unmodified FCG with a double stack (Colt/Uzi) configuration.
-All other upper parts can be standard but there’s some aftermarket stuff you can add that’s 9mm specific.
-A standard 5.56/300BO/”MULTI”/whatever you want to call it lower with whatever bits you want in it.
I could probably make this an article if anyone here is interested. Not a ton to it really, but it’s worth knowing.
Very interesting article and great discussion! Very true that buying/building a PCC costs as much as a case or two or 5.56, benefit may be if you want PCC+handgun to share mags for home defense, competition, SHTF or whatever, or shoot enough short range that the ammo savings would add up. PCC’s are also just plain fun, close to a SMG and can maintain very similar manual of arms to normal rifle. Can be crotchety to get to run reliably tho. Great fun and accurate enough for paper plates and steel at <100yds, 2-3 9mm rounds for price of 1 5.56, and less spalling off steel at close ranges.
I found the Aero Precision EPC-9 series uppers Last-Round Bolt Hold-Open feature works great with a minimal adjustment, but the barrel feed ramp won't feed anything except round-nose bullets, jams all hollow points and wadcutters deep into the brass. I like Stern's glock-cut BCG and KAK's 9mm AR15 Configurable Buffer Kit – tuning 22-24oz BCG+Buffer combined weight was critical (my DIY AR-9 flung shells 30+ft, bolt velocity was waaaaaay too high, smashed up the bolt catch real bad, and recoil was worse than 5.56 until i tuned mine to 23ish oz. 3oz standard 5.56 buffer and 5.3oz H2 buffer werent nearly enough).
S&W Response just came out, i think its a 16" AR pattern rifle for around $700, comes with interchangeable mag wells that can use either M&P or Glock mags. Maybe theyll sell it as a stripped lower one day. Angstadt Arms has the AXL-9 stripped lower coming out soon, that will have interchangeable mag wells for M&P, P320, Glock, CZ and eventually more, but will probly cost a ton. Dedicated-mag lowers are great if you use a handgun with same mag, but maybe not if youre invested in 2 or more ecosystems (ex Glock + Sig platforms). Matador Arms Mag-X, KAK, and Stern Defense MAG-AD series mag well inserts let you run Colt Glock Sig CZ M&P and maybe Beretta mags in a standard 5.56 lower and keep the ability to change it back to 5.56 (youd need 9mm upper, mags, and very heavy buffer to convert to 9mm) and the Stern has last-round bolt hold-open (i have no idea if a lower's LRBHO would interfere with an upper's LRBHO?) And obviously the Endo Mags dedicated mags + upper + real heavy buffer is the simplest temporary conversion if you dont mind single-purpose PCC mags.
* forgot to post, Blowback9 dot wordpress dot com helped me figure out alot of problems with my DIY AR-9, great source of knowledge
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