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9mm AR's

Discussion in 'The Workbench: Builds And Modifications' started by John A., Oct 30, 2017.

  1. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    Several years back, I built a 9mm AR upper.

    In that time, I've learned a bunch about some of the quirks with them.

    Ramped bolts

    very heavy buffers and springs

    Receiver pin holes egging, and pins breaking.

    In short, I've learned several things that helps the guns do better that I'm going to share to maybe help someone else.

    I admit that I don't have any hands on with the new glock lower variant and while interested, I'm pretty content with the setup that I am running now and see no real reason to change anything. Especially since I don't own a glock and I have a few uzi mags since I have 3 guns that share mags.

    The bolts on the glock kits have a more narrow bottom shelf to fit between the glock magazine feedlips. This much I know. And to my knowledge, there are a few "hybrid" bolts that will work with either style upper, but I'm not getting into the critical details and differences of the 3 major types of 9mm AR's. (Colt style, Olympic Arms variant, and the newer Glock style).

    But for this topic, I'm going to concentrate on what I have done to my Colt style conversion to maybe help someone who's considering building one to help them save a lot of headache to give a few options they may want to consider.

    The main reason why I went with a Colt style was it was the most common at the time. I appreciated the fact that I can use several different kind of magazines in it. And as we all know, a magazine will make or break the gun and can mean the difference between one working like it's supposed to or a jam-o-matic.

    MAGAZINES

    There are Colts/Metalform magazines (which have proven themselves as good quality and are generally held in high regard).

    Second up, is the IMI 9mm Tavor magazines. I think these are just as good of quality as the Colts, and they are about $8-$10 cheaper. IMI stuff is all good stuff. The Israeli's don't screw around about the quality of their stuff. And like the Colts magazines, have a bolt hold open follower.

    Next are modified uzi magazines. These are also well known good quality but don't lock the bolt back on the last round. And standard uzi mags will also need a notch milled in them to accommodate the AR mag catch. * The IMI Tavor 9mm mags I mentioned earlier do have a bolt hold open follower and are ready to go in an AR9 out of the box and why I mentioned them first.

    And there are other numerous "average" quality mags out there too. ASC, Cproducts, Promag and I'm sure there are probably some others too that have slipped my mind over the years.

    RAMPED BOLTS

    These are the most ideal due to reducing the amount of force exerted on the hammer because 9mm blowback is a lot worse in an AR than 556 and other rifle calibers.

    Reducing the initial pressure on the hammer also reduces the pressure exerted on the hammer pin, the receiver pin holes (egging out the aluminum) and feels better when shooting it too. It is not too uncommon to hear of a broken hammer pin, especially with incompatible parts combos.

    KNS PINS

    I like to use Anti-rotational pins in my 9mm lower. For one, they are stainless steel, and for the other reason, the pressure is distributed on both the hammer and trigger pin holes rather than the brunt of the force being on the hammer only.

    BUFFERS and SPRINGS

    There are several different combinations that you can use. I'm not going to pretend that one is "the best" over the others. But here is why I am listing these two first.

    The 9mm AR bolt doesn't have to cycle as far rearward as a rifle due to the length of the cartridge case itself.

    So, to reduce the amount of travel that the bolt has to go, and also to reduce the possibility of the bolt breaking the bolt catch because it has a massive run-n-go that isn't necessary, I recommend the Spikes Tactical ST or the New Frontier Armory Extra Heavy buffer

    Both of the buffers I mentioned above are longer than a regular 9mm carbine buffer which reduces the amount of unnecessary movement that I mentioned earlier, and is heavier than a standard 9mm buffer.

    I think it's pretty evident why I think it's the best option for anyone who is just starting their build.

    For those of us who don't want change their buffers, it's best to use the heavy 9mm buffers that exist, but in order to reduce the travel, you can add enough quarters in the rear of the buffer tube to take up the unnecessary space in there behind the buffer spring, or you can install an aftermarket buffer like the New Frontier Buffer Spacer or Spikes ST-9BS.

    Another option for those of us running standard 9mm buffers and buffer spacers is to add a +power buffer spring from Wolffe or Springco

    Naturally, those options all take will all need tuning to your setup.

    MAGAZINE BLOCKS

    In order to use 9mm mags in a standard AR15 lower, you have to use a magazine block. Or, a dedicated 9mm lower receiver.

    But since I'm using a 556 lower, obviously I had to use a conversion magazine block.

    Prices range from ~$50 for the plastic promag mag block up to ~$200 for the Hahn mag blocks. There are several other brands that are priced in the $100-$150 range.

    The magazine block that I have was made by AMM, but to my knowledge, they are no longer selling them.

    Mine was a top load model, and would occasionally want to "move around" inside my magwell with use or external pressure. Especially when "smacking" the mags in making sure they're seated properly.

    So, I went a step further and "affixed" it to my lower via a long roll pin that went through the standard magwell and through the mag block itself and also used a set screw that I put in the front of my magwell that is hidden behind the front pivot pin lug.

    In order for it to come out now, the upper has to be off of the lower to access it because the lug would prevent it from moving while assembled. I just never fully trusted the tensioning worm screws would never move at the worst possible time. Especially since they did.

    This was more for reassurance that everything is going to remain exactly the same place with no risk that the mag block is going to change positions, which could cause feeding problems. This is just one of the ways that I go above and beyond "commercial standards" and when I make something that I may have to depend on for life or death, I don't want any shortcuts in my stuff.

    [​IMG]
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    MAG CATCH

    Another common occurrence with 9mm conversions in a standard lower, is often times the magazine catch is often "too short" to hold some 9mm mags in the gun. They'll occasionally just drop out with no rhyme or reason.

    There are a few things that you may do to remedy that. Screwing the mag catch and the mag catch button as far together as you can. That may help a little.

    You may can weld the tab of the mag catch and file it down so it doesn't grab on the follower or spring as you're shooting to give it more surface area,

    or Spikes Tactical and RRA do offer a 9mm mag catch that is profiled a little differently than a standard AR mag catch and the thinner profile allows them to protrude a little deeper in the mag body.

    Since I have already typed more than I had planned to, I've not added any specific photos of commercial products, but I did highlight some of the key words for you to be able to research for yourself if you're interested.
    95jza80tt, MikeD, Scoop and 1 other person like this.
  2. Djcala

    Djcala 20g Supporter

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    Very informative as always. Enjoyed reading.
  3. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    Thanks buddy. A lot of folks are getting into pistol caliber carbines (AR's specifically).

    Pistol cal AR's are different from their standard AR counterparts in several aspects, and many folks avoid them because of that reason.

    So, for anyone considering building or buying one, I thought that having all this info in one spot may help someone and save them some aggravation.
  4. dieselmudder

    dieselmudder .308 "Philanthropist"

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    Good info John. It condenses much research. And trial an error. I do plan to have one in the future.
    John A. likes this.
  5. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    Jump on in. The waters' fine ;)
  6. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    Temperature is pretty cool this evening, but I wanted to do some quick load testing while I had the time.

    I'm still wanting to try some 165 gr pills because they're supposed to be quiet, but for now, the 147's will have to do.

  7. Water Monkey

    Water Monkey The man, the myth, the monkey Forum Moderator Supporter

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    I love you. I'm making moves Black Friday and Cyber Monday on a build.
    John A. likes this.
  8. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    Considering your locale, is it easy for you to get glock mags?

    I would assume that finding neutered colt mags will be more difficult to find, so that may need to taken into consideration.
    Water Monkey likes this.
  9. Water Monkey

    Water Monkey The man, the myth, the monkey Forum Moderator Supporter

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    Yeah. I'm going with a dedicated glock lower and BCG.
  10. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    That would make sense.

    There are several options for glock style at the moment.

    PSA, angstadt arms, new frontier armory, freedom ordnance and probably others too.

    I've considered doing one, despite my overall dislike for glocks, just to have a couple of 50 round drums for it. Even considered doing one from an 80.

    But I've been plenty content enough with mine the way it sets.
  11. Water Monkey

    Water Monkey The man, the myth, the monkey Forum Moderator Supporter

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    I've been doing a fair amount of research the past few months. Gonna be a fun gun for me and a more defensive rifle for the wife as a HD rifle rather than grabbing her glock or 590A1.

    I was leaning angstadt arms but QC 10 is a little cheaper and set the standard for PCC AR designs.

    I dunno. Whoever has the better sale will get me really.

    Kinda leaning away from the Palmetto arms build. Though that would be a decent budget way to go.
  12. Djcala

    Djcala 20g Supporter

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  13. Water Monkey

    Water Monkey The man, the myth, the monkey Forum Moderator Supporter

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    Dude. I've been trying to effing resist the jack. But it does call to me.

    Let's see if the sales are decent. It's not off the table.
  14. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    You guys know me pretty well. I like a lot of pistol caliber stuff.

    I hadn't heard of quarter circle until fairly recently. I got introduced to pistol AR's in the late 80's or early 90's when the only two choices were Colt style and Olympic Arms style. I'm not sure if QC10 has been around long enough to set the standard for anything yet.

    But, the glock style does seem like a nice variant. Especially for people that already have a lot of glock mags.

    I'm jonesing for a 45acp AR, but probably isn't going to happen any time soon.

    I was seriously wanting a 7.62x25 upper for years too, until surplus ammo dried up and the prices spiked.
  15. Water Monkey

    Water Monkey The man, the myth, the monkey Forum Moderator Supporter

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    Interesting. I ran across this video a while back and he went over the progression of the 9mm AR designs. He talked about QC10 around the 14 min mark.

    Curious if he's on point or just hot air. Thanks John

  16. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    I watched the first half of the video or so. Paying attention to what he was saying.

    I found everything to be truthful and spot on.

    I also didn't know that QC10 was doing some of the things that they are.

    Longer buffer being one. The machined feedramp being another. Sounds like they've worked through some of the older issues up front and applied that to their product line.

    Only thing I think they could improve on would be to do a delayed/roller lock action, without the buffer tube and probably design their proprietary upper recievier for that and with a side folder stock. It's certainly do-able, and would even be preferred for a lot of things. But few people are going that route these days. Even the Sig and Scorpion and most all other 9mm's are standard blowback. Not knocking that specifically because if ain't broke-don't fix it, but delayed blowback is still ideal for what/how I shoot. Perhaps even a non-reciprocating left side charging handle, but if it has a side charger, it would HAVE to have a moving charging handle cover to keep gas inside the receiver and out of my face. But I suppose it off topic and getting more into a wish list type thing.

    Another thing he mentioned is the actual machining of the guides on the feedramp.

    My mag block was based on the 2nd gen colt style that he showed earlier in the video. And yes, I have roll pinned mine in the receiver as well. I wasn't about to pin it in my SBR lower. That was another reason why I built up a dedicated pistol lower for it because I enjoyed shooting it a lot, but I didn't want to be poking holes where they shouldn't be on my registered lower. My mag block wasn't really moving around, but I didn't want to risk it either. If I'm going to make something and put my name on it, It's going to be right. And why I pinned the mag block in place in the pistol lower.

    I also didn't know that qc10 was machining guides in their feedramp. I did that to mine as well. It was really a no brainer for me. After shooting mine suppressed, obviously it would get fouled around the feedramp/chamber after a few weekends of heavy shooting.

    I could see physical "tracks" of the bullet path on the feedramp. So, I used those tracks as a guide to where to machine my guides when I did mine. There was no guesswork to it at all. A few minutes with a small round file, and away you go.

    feedramp 001.JPG

    Whether Colt had a problem with theirs or not, I don't know. But I know that I don't. Mine has feed every bullet taper that I have ever tried through it with no problems.

    Though I'm going to say it now, 9mm guns, especially in double stack magazines, prefer round nose bullets.

    The 9mm was designed with round nose bullets, and some that have long tapers and deep hollowpoints, may choke in some 9mm guns because it's too far away from how the gun was originally designed.

    Single stack mags don't seem to have those issues as much because they feed pretty much straight into the chamber from the mag and not from an angle like doublestack mags do, so you really have to test a gun to make sure what ammo you can use but that goes without saying about all of them.

    Spikes Tactical makes a longer buffer to eliminate the overtravel, which the guy in your video said he recommended to Colt after a cartridge had made a stoppage in the fire control pocket.

    After speaking with spikes about their bolt, I don't know that mine would benefit from using it. I already am using a spacer/buffer made of polymer and I am happy with the way mine feels and shoots. You can tell the gun cycles better with it. By "better", I mean, the stroke isn't as far, it's back in battery quicker, and obviously, no broken bolt catch.

    The longer Spikes bolt that I looked at came in at 8.5 oz, and the one I am using is 5 point something oz. 5.3 maybe? 5.4? I don't really recall off the top of my head.

    But, I'm also using an extra-heavy spring in mine and again, right now I'm happy with how it shoots. Bolt stays closed well. minimal blowback. No gassing at all to the shooter, which take my word for it, that's impressive shooting with a dedicated can.

    I have decided that when I wear out my spring, I'll get one of the spikes longer buffers (if they're still making them then) or I'll get a piece of rod stock and make my own. But for the meantime, I'm fine with it how it sits.

    I don't really consider any other to be superior to the way I have mine set up, and I guess since the QC10 does all the work up front, I would give it the nod because I've worked on mine a lot from how it came out of the box to get it where it is right now. Otherwise, it's just another route to get to the same place and I wouldn't give a second thought to grabbing mine tonight if need be.

    Also, not to be condescending, the footage of him shooting his can, I'd be checking my can for problems if it was as loud as his. That's pretty raunchy. Unless it's 115 gr supers shooting into a nearby berm.
    Scoop and Water Monkey like this.
  17. Water Monkey

    Water Monkey The man, the myth, the monkey Forum Moderator Supporter

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    Thank you @John A. I appreciate the time you take to explain things. Makes me understand it much better.

    Raul
  18. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    I just hope some of this info helps someone.
    dieselmudder likes this.
  19. Water Monkey

    Water Monkey The man, the myth, the monkey Forum Moderator Supporter

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    So I've started. The process. Got a rail. Back up sights. Carbine buffer tube set.

    Looking at a Wilson 9mm stainless steel barrel. See if I can get one for sub $100.

    See what Black Friday brings between QC10 and angstadt.

    Torn between a thordsden stock or one of them weird grips. Think the thordsden is the way to go like my last AR build.
    Last edited: Nov 16, 2017 at 7:30 PM
    John A. likes this.
  20. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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