So I was in my LGS earlier and they had a bunch of stripped AR-9 lowers for sale with glock magwells. They were $125, plus $5 background check fee. I was kind of on the fence, I have a couple of gun projects going on and I wasn’t really looking to start another one. Then he said he’d throw in a 4.5" barrel for $40.
I don’t know who made the barrel but they mill their own lowers and they are good quality that I have used on other builds.
What would you do? The price is right I believe but I don’t know if I want another project, especially an AR-9. Anybody have any feedback on using an AR-9 with a short barrel like that?
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I’d do it, but I’m biased
I’m building an AR9 with my PSA Ghost Gun lower
4” PSA upper, should have it mid next week
I plan on running the EndoMag 9mm Pmag drop in. I won’t run Glock mags unless that becomes my only and final option
Also building an AR47 rifle…
I think why I am hesitating is that I do not know a AR9 like I know a ‘regular’ AR. Blowback system, what type of BCG, what type of buffer weight, LRBHO, some uppers don’t work with some lowers, glock mags or colt mags??
Alot more to wrap your head around. There is no gas system so there is that.
Here’s what I am thinking if I do it, tell me where I am wrong…tell me where I am wrong. Need an upper w/bcg, buffer system with a heavier buffer 8-10 oz, dedicated 9 mm lower (the one I saw earlier), glock style mags.
Same here, but I’m diving in. I want a 9mm AR, but without a magwell adapter for Colt or Glock mags.
And I’m certainly experimenting. The PSA BCG is a hybrid for 9mm. I plan on running the Armaspec SMB for 9mm. With the MEAN 9mm conversion for Pmags, I haven’t seen anyone publicly posting about running this configuration, and what I plan to build.
I’m not sure if my build plans will work, but I certainly look forward to learning and making this work, if at all possible. I like to learn and tinker.
Same for my AR47 build. PSA recommends an AR10 buffer spring in this AR15 configuration. I plan on running an Armaspec AR10 SMB instead. It maybe the golden ticket, or I may regret it.
So I can tell you what I plan on doing, but don’t necessarily follow my advice . 
Only thing I would caution you about the Armaspec SMB, their website says:
“ 9mm Bolt Carriers ONLY: For proper function of the SMB-9 in your 9mm rifle or pistol, the extra weight on the back of the bolt carrier needs to be removed. It is held in with a spring pin. Will only work with BCGs that have the extra weight inside and removing it will not shorten the BCG.”
They need that pinned weight removed so the SMB’s guide rod can pass into the bolt carrier.
IMHO, removing the weight from the bolt carrier may not be the best idea. Blowback ARs need added buffer weight not less and the SMB weight is lighter than most guys run already. I would choose a deadblow buffer closer to 9 oz or more, especially if you’re adding a suppressor.
I have a 3” upper on an AR9, I wouldn’t hesitate to buy a 4.5”. 9mm ARs are fun to shoot! On my first one I used Endomags, the rest of mine are large or small Glock compatible depending on the caliber, I don’t really see a difference except I can fit several 33rd Glock mags in my pocket, the Endomags take up more room. Glock mags for me from now on!
I’ve noted that in my build plans, and that’s why I haven’t bought it yet.
My educated guess is that their SMB makes up for that lost weight. Their 9mm SMB weighs almost 10oz, giving it the equivalent buffer weight of 6.9oz.
I can also chuck that pinned BCG weight up in a lathe and drill through the center for the SMB center rod to pass through, and use two staked roll pins to secure, still leaving the center hollow.
I’ve put some thought into this.
Edit…I had to do the same with my buffer extension for my Sylvan Arms folder on my 300BO pistol.
Safes are full and I swore no more builds…where is this shop with that special? A friend wants to know.
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OK, at the risk of drawing the ire of the folks in the room, I am thinking about getting that lower, building it out. Then topping it off with a Bear Creek 9mm buffferless upper. Now before y’all spread your cheeks and dump on me, I have a BCA .22lr bufferless upper with a 10.5" barrel and that is fun as heck (and cheap) to shoot.
I’d still get the barrel for a future build,
Just thinking out loud.
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So I did it, I got the lower for the AR9 with the 4.5" barrel. Got online last night and ordered all the parts to build it. Planning it out is a little different for picking out parts but not much. The one thing I learned is that the weight of the BCG and the buffer should be at least 22 oz.
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What? I’m all ears. I’d love a bufferless 9mm upper due to the pistol brace “rule”.
Pistol braces are the ONLY reason I have an AR pistol. Without the brace a AR pistol looks like it belongs on the short bus. I hate my AR pistol now. I dont even want it anymore lol.
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Here’s a pic of my .22lr 7.5" bufferless upper. 9mm looks the same, choose your barrel length.
pic
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I dont understand the point of an ar pistol in a pistol caliber without some sort of stock on it… wouldnt you rather just have a normal pistol?
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Nope
I’m building an AR9
Adding to my 300 Blackout pistol
Very excited to complete the AR9
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I have normal pistols. I am a gun enthusiast, I like both building or assembling, depending on the project I have at hand. My AR pistols are just a variation that I find fun to shoot.
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I’m 100% out of the AR Pistol business , Not because of the BATFE, because I found the whole concept pointless.
I have Rifles and Carbines in the AR family to spare. I even have a Colt AR Carbine Chambered in 9mm×19 that I rarely shoot…but when I do? Its goes bangiddy bang without hesitation every time.
I have pistols galore. I figure I’m better served by mastering them , than playing with something thats more of a novelty or hedge and laced with Sort me Out problems beyond that of its Carbine or Rifle brethren historically.
Count Me Out on AR Pistols in any Caliber…especially a Pistol Caliber.
I would own a Department of Energy DOE 9mm SBR in a Skinny Minute… only because they are Uniquely designed and equally rare.