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[Review] Mean Arms EndoMag Conversion Kit

Want to shoot 9mm out of your AR-15 but don't want to get a completely new rifle? We review Mean Arms' EndoMag which turns your 5.56 lower into 9mm.

    Pistol Caliber Carbines (PCCs) are all the rage right now and for good reason.

    They’re cheap to shoot, wicked fun, and great for training fundamental skills.

    Buying a whole new rifle, while exciting, isn’t always in the budget.

    EndoMag Group Pic
    Mean Arms EndoMag

    But converting your current rifle might be!

    EndoMags from Mean Arms take a standard Magpul magazine and convert it from 5.56 NATO to 9mm allowing you to just change the upper on your standard AR-15 and BAM you’re ready for some PCC plinking fun.

    You should take a look at our video and if you liked it, don’t forget to subscribe!

    Table of Contents


    What Is The EndoMag?

    This part is simple, really everything about it is simple, the Endo Mag is a conversion kit for standard Magpul magazines to turn them into 9mm mags.

    EndoMag Lips
    EndoMag Feed Lips

    Endo Mag has a great video on how to do the conversion, so we’ll leave it to them to explain that part. From our end, the conversion is super easy, quick, and works great.

    at Brownells

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons

    Once your magazine is converted, you just load it up with 9mm, and load it into the standard AR-15 mag well… And that’s it really.

    You’ll need a new upper also and if you’re looking for a budget option we highly recommend Palmetto State Armory 16″ 9mm Complete Upper.

    Best Budget 9mm Complete Upper
    at Palmetto State Armory

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons

    Mean Arms does recommend that you do a bit of break in so that your mags and BCG mesh well together. Personally, I didn’t know about this step my first time and didn’t have an issue – but on the other mags, we did the break in.

    Restricted States May Apply

    Normally anything fun on the firearms market is not available to those of us that live in less-free states, but Mean Arms actually took that into consideration when they made the EndoMag.

    EndoMags ship with a 10-round limiter built into the assembly, but also make it very easy to cut that limiter down to 15-rounds or remove it granting you access to the full 30-rounds.

    endomag snip tab for freedom
    EndoMag, snip tab for freedom!

    That’s the kind of community I like to see in the firearms industry!

    Range Report

    Testing got cut a little short due to a sand storm that rolled in, but during the testing, we had literally zero problems. All three magazines worked with all 4 lowers and 3 different 9mm uppers in every possible configuration we could make.

    endomag tested options
    Some of the EndoMag tested options!

    Every combination of uppers and lowers we tried simply worked. Period.

    That kind of flawless function is really rare to see with niche products like the EndoMag – props to Mean Arms!

    Uppers Tested

    Two different PSA 9mm uppers and 1 Franken upper made from a Rainier Upper and Lead Star Arms barrel.

    EndoMag tested uppers
    PSA 9mm Upper (top) and Aero Precision/Lead Star Arms upper (bottom)

    It should be noted though that all of the testings was conducted on PSA Gen 4 Hybrid 9mm BCGs. EndoMags can be used with most 9mm BCGS, but there is some possibility that your mileage may vary.

    at Palmetto State Armory

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons

    Lowers Tested

    Two lowers were from PSA rifles, one from Aero Precision, and the last was BCM.

    Two Lowers EndoMag
    at Brownells

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons

    Triggers included Elftmann 3-Gun, PSA Precision 2-Stage, BCM Stock Trigger, and a Rise Armament Super Sport.

    None of the triggers presented an issue, all of them just ran perfectly.

    Tested AR-15 Triggers
    Read about these triggers and more in our hands-on testing!

    Charging handles, safeties, and more all varied but none of those should present any change in reliability. We used standard carbine buffer weights and springs for all of the lowers, the same ones we use when the lower is shooting 5.56 NATO. And… there isn’t much else to say, everything ran perfectly.

    Who Is It For?

    If you want to test out PCC shooting or you want to just try something new with your rifle or you really like your current lower and don’t want to build a whole new one, EndoMags are perfect for you.

    Shooting EndoMags

    Personally, I really like them because they are just handy to have and use. I can keep a few PMAGs set up for 9mm, and then just switch uppers when the mood strikes.

    What might be best of all is that this is a very economical way of getting into the PCC world. A new upper will run around $300 or less, the EndoMags are roughly $30 each, plus $12 PAMGs. For under $350 you can build yourself a PCC using your normal AR-15 lower.

    at Brownells

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons
    Best Magazine
    at Gun Mag Warehouse

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons

    Bang for your buck, that is a steal of a deal!


    I didn’t have any. Weird, I know, but I just didn’t have any issues with it. Everything worked perfectly. The mags were easy to install, easy to load, easy to use. My rifle never failed and I had a blast.

    There are three things that you should keep in mind.

    The Trigger

    One of the flaws with any 9mm blowback AR system is that they are inherently rougher on triggers than 5.56 NATO is. Madness, I know, but it’s true.

    The direct blowback action of 9mm uppers means a harder impact on the hammer and more energy transmitted into the trigger pack. This can cause pins to walk or parts to break.

    BUT this really isn’t an issue for most triggers, normally it’s the higher-end race triggers that are finely tuned that run into this issue… We know because we’ve broken a trigger before on another 9mm set up!

    Timney Competition and Calvin Elite
    Timney Competition and Calvin Elite

    That said, any PCC rated trigger won’t have this issue. And most mil-spec or duty triggers won’t either. But if you have a real nice 3-gun trigger in your lower, you might want to check with the manufacturer before throwing a 9mm upper on it.

    Clearing Your Rifle

    Not so much a con as just a quirk of design. Because the EndoMag acts as its own ejector, you need to leave the magazine in to extract and eject a round from the chamber.

    If you want to do this with rounds still in the magazine, you need to rack your charging handle back, press your bolt hold up to lock your bolt, release the magazine, and then close the bolt.

    If you just want to clear the rifle at the end of shooting, you need an empty EndoMag in the magwell to do so.

    Otherwise, you might extract a round and rechamber the round without ever ejecting it.

    The Looks

    Part of the fun of a PCC is the look of a PCC, and this can’t be ignored. A big ‘ol Glock mag sticking out of a AR-9 lower just looks awesome and is fun. That isn’t something you get with the EndoMag.

    AR9 Colt Wide View
    An AR-9 using Colt magazines, read about that build!

    Is that a con?

    Kind of? It’s something to consider, and something to consider is that this might be a gateway gun. Once you find out how awesome a PCC is, you’ll be building yourself a lower soon after!

    Best budget AR-9
    at Palmetto State Armory

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons

    By The Numbers

    Accuracy: 5/5

    Accuracy was unaffected by the EndoMag, so as long as your upper is accurate you’re good to go.

    Installation: 5/5

    It really is super simple. As long as you’ve taken a magazine apart before, nothing will be new to you.

    endomag guts
    EndoMag, PMAG, and more

    Looks: 2/5

    It takes away from that awesome AR-9 vibe we love about PCCs, but that’s the price you pay for using a cool conversion.

    Customization: 5/5

    Since this is the customization, the sky is the limit. Lowers, triggers, uppers, barrels, optics, if you can do it to an AR-15 you can do it to an AR-15 loaded with EndoMags!

    Bang For Your Buck: 5/5

    Hands down the cheapest way of getting into the PCC world. Awesome.

    at Brownells

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons

    Overall Rating: 4/5

    Parting Shots

    Is the EndoMag for everyone? Yes and no. If you want to go deep into PCCs, then you might want a dedicated lower. But if this is a plinker, training aid, or just trying something new – then it makes a lot of sense.

    And it’s just so fun!

    All said and done, I really like the EndoMag. It was reliable, fun, and great to use. I’ll be picking up some more soon.

    What is your PCC set up? 9mm, .40 S&W, or .45 ACP? Let us know in the comments! If you think you want to jump into the deep end, read about the Best Pistol Caliber Carbines!

    wilson combat pistol caliber carbine
    Wilson Combat Pistol Caliber Carbine. HOT!

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    14 Leave a Reply

    • Commenter Avatar

      I personally hate the way a Glock mag sticks out of an AR lower. It just looks goofy to me. Now, if they ever make a mag well converter for Scorpion mags, that would look good to me

      July 14, 2021 10:50 am
    • Commenter Avatar
      Mike B.

      I have a PSA 5.56 lower and a Delta Team Tactical 9 mm upper. I'm using Endo mags, but I am having a real problem with LRBHO. It just won't lock the bolt with an empty mag. Any suggestions?

      September 22, 2020 9:27 am
    • Commenter Avatar
      Mordechi Cockey

      I have a Glock and Colt dedicated lowers with their respective uppers running SBR on both. I have just ordered the Endomag and cant wait to throw it on my SBR lower. If it runs well then I will add it to my collection of PCC.

      February 7, 2020 12:06 pm
    • Commenter Avatar
      Jeffrey Rada

      I purchased a three pack of the Enodmags and they work great! I have used them twice in a competition and have not had a failure yet. This allows me to convert from 9mm to 5.56 or 300 blackout with just the upper, bolt and buffer springs being swapped.

      December 4, 2019 9:05 am
      • Commenter Avatar
        Bryan Williams

        What weight buffer did go with for your 9 upper?

        December 11, 2019 8:16 pm
    • Commenter Avatar
      Ian VanVranken

      Great article, would love to get these vs a mag Conversion block. Also, you guys should mention the cmmg 9mm conversion that mean arms makes mags for, from what I've heard, the radial delayed blowback shoots a lot nicer than straight blowback. It's a step up in budget though, so one day I'll probably start with these and move up to that later...

      December 4, 2019 8:45 am
      • Commenter Avatar
        Ian VanVranken

        And finally when I move up to a dedicated lower, I'll go with a quarter circle 10 that takes MP5 mags!

        December 4, 2019 8:47 am
    • Commenter Avatar

      Great review and looks like a great alternative. I like the idea and looks of sticking with a PMAG. My personal opinion is that the long “stick” mags in PCC’s look a bit strange so I’m exited about this option to break into the game.

      December 4, 2019 2:38 am
      • Commenter Avatar
        Ian VanVranken

        I was just about to say the same thing about the looks...

        December 4, 2019 8:40 am
    • Commenter Avatar

      Article is MUCH TOO LATE for me!
      For 2 years I've have a PSA 9mm lower, a $300 16 inch free floated barrel upper (handguard is round with no accessory attaching points) from Brownells and a PSA 9mm bolt. It uses ANY Glock 9 mm magazine that fits a G17, G19, G34 INCLUDING the 33 rounder. I would like to replace the PSA trigger because it's too heavy. Anybody have suggestions?
      Shooting it is great fun and it seems to recoil MORE THAN my 5.56 AR-15s!

      December 3, 2019 7:00 pm
      • Commenter Avatar
        Gabriel Simmons

        Try a SSA or a LMT two stage trigger

        December 4, 2019 8:07 am
    • Commenter Avatar
      Elven Ray Clemons

      I am in the process of building my first ar15-9mm. I decided to go with a standard ar lower and use the endomags. Great video and looking forward to making my own test. Ray

      December 3, 2019 5:40 pm
    • Commenter Avatar
      Dustin Tran

      Im surprised that you were able to get away with using standard carbine buffer and spring. From what I've researched online, many recommend a much heavier buffer weight. Some even heavier than H3, like a 7.7, 8 or ever 10oz. What kind of round counts have you done with the above configurations?

      December 3, 2019 3:44 pm
      • Commenter Avatar
        David, PPT Editor

        Combined across all of the rifles was around 500, we got cut a little short due to a dust storm that rolled in on us.

        December 3, 2019 4:24 pm
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