Building an AR9

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DMW1116

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I’m looking either a pistol or 9mm carbine for my son. I’m was thinking we could make it a project.

So I have a minimal experience building ARs and have put together 2 lowers for standard calibers.

I was looking at a Spikes 9mm specific lower and a PSA kit. Is it basically the same as a regular lower build? The kit has the upper already assembled.

Many lowers don’t have last round bolt hold open. Evidently this one does. Is there a reason it’s not everywhere?
 
If you look at the Aero precision EPC9 uppers they have last round hold open built into the upper so if you get a lower with out it there upper will help out.I would recomend getting a lower with LRBHO if your starting from scratch .I think that the lower with LRBHO is the way to go, but just my opinion.Good luck with the build you will love the 9mm ar no recoil cheep to shoot.
 
Assuming that’s the route we go I’m planning on a dedicated 9mm lower and a 16” barrel. That what you meant right? A dedicated pistol caliber lower j stead of a normal one and a mag adapter?
 
I know what you mean about the velocity. I’m already looking for loads to push past 1500 fps.
 
My daughter and I built this one using a standard upper and standard lower with the Stern Defense magwell adapter for Beretta M92 mags-
IMG_20200628_223935_4.jpg
It was a fun project and runs great (she specified that it must have a bayonet lug......) with a H1 carbine buffer
Very occasionally, a 9mm case will get wedged vertically in the ejection port- this is why I do recommend using a dedicated 9mm upper with a larger port.
I also have a PSA carbine with dedicated upper and Glock-mag lower and it had some trigger-reset failures at first, but after cleaning, lubing and 100 or so break-in rounds, it has been 100% since.
 
There is nothing special assembly wise other that using the correct parts, but just be aware that depending on what combination of parts you decide to use that there may be some fitting and parts experimentation required to get everything playing happy together. Blowback AR’s need some tuning to get the buffer weight right and cycling at the right speed, and some configurations are better than others for feeding reliably, so don’t be too surprised if it doesn’t run like a clock the first time out.

I like a lower with a pistol brace and an 8-10” barrel.
 
I thought about that but with the uncertainty of the brace rule I decided to go with a full length rifle.
 
It looks like you've settled on a Glock pattern lower. I chose to go the way of a Colt pattern. I had no reason to go with Glock mags and I think the Colt style mags look cooler.

Just some food for thought. Some bolts don't play well with milspec hammers and require a 9mm specific hammer. Whatever that means. It's just an issue I ran across on the internet. I never experienced it. When I decided to dip my toe into the PCC world, I went the cheap route.

I have uppers laying all over the place, so I went with a mil spec upper and standard charging handle. I got a Faxon bolt. I went with this bolt because it is compatible with both Glock and Colt pattern lowers and works with a standard milspec fire control group. I also got a Ballistic advantage 5.5" barrel. I got a cheap free float handguard from AR15handguards and put it all together.

Since I was just dipping my toe, I got a few Endomag inserts that slide into PMag bodies. With the parts I've listed, the inserts worked 99%. They didn't like hornady hollow points. When I decided that I liked it, I got one of those inserts that slides in from the bottom for around $50 and just dedicated one of my lowers to 9mm duty.

It runs like a clock.

Oh, and don't tear your hair out about which buffer you should go with. Just go with a Vltor stainless A5 buffer. They are the correct length and less expensive than the insane prices some charge for a good 9mm buffer. The Vltor part numbers start with A5SH and come in different weights. A total of about 22 oz. for bolt and buffer is where you want to be. As for springs, I use a Sprinco blue although I know a few that opted for the red.

Honestly, I built it because 5.56/.223 got so expensive and 9mm was still kinda cheap when COVID hit. Now, 9mm is pretty expensive. I just ordered 1000 rds of 9mm and it was almost as expensive as 1000 rds of steel case .223. I don't think I'm gonna be shooting to much 9mm out of my AR in the foreseeable future.

I also saw a comment above that an AR9 has no recoil. I don't agree. An AR9 has more recoil than an AR15 in 5.56. Blowback vs gas operated.
 
I haven't messed with Glock style 9mm AR lowers, but they should be the same as Colt style lowers when it comes to buffer weights. 5.5 ounces is the minimum for a blow back 9mm and most will run a buffer the weighs around 7.5 to 8.5 ounces.

I went with a Colt style lower when I built my 9mm AR since I was wanting a Colt SMG clone. Plus with the Colt style, there is no need for any added mechanisms for the LRBHO to function.

TonyAngel said:
Just some food for thought. Some bolts don't play well with milspec hammers and require a 9mm specific hammer.

I also saw a comment above that an AR9 has no recoil. I don't agree. An AR9 has more recoil than an AR15 in 5.56. Blowback vs gas operated.
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9mm bolts not playing well with GI triggers is a thing of the past for most manufacturers. The 9mm bolt needs to be ramped for a mil spec GI trigger and mot manufacturers of 9mm bolts cut the ramp so there should not be any issues there.

And I have to agree that a blow back 9mm has a bit more felt recoil over a gas operated AR chambered in 5.56/223. The 9mm blow back recoil isn't bad but it is more noticeable.
 
Oh, as for the power of the springs. I don't choose my buffer spring to minimize recoil. I choose it so that my muzzle comes back down on the target and not passed it. Too much spring and it's like having a compensator that overdrives the gun. You'll be picked the muzzle up for follow up shots.
 
Seems like all sound advice. I plan to check PSA later today. They have a retail store near my office. I also have a local cohort who’s built 4 AR9s so I’ll talk to him too.
 
I have a 10.5" upper dedicated pistol lower, from PSA, Glock style.

Unfortunately, PSA buggered up the detent pin, so I've only fired it once. :fire: It did prove accurate and mildly recoiling at that session, though- the blowback is felt more than .223, but still not bad

John
 
So I've done the ar9, the cz scorpion, and a cmmg banshee. In that order. And the banshee is far and away the best. I used a barrel and bolt from cmmg, the built out the rest using standard at parts. The barrel and bolt cost $150-200 more than regular ar9 parts, but it is worth it. The radial delay blowback lessens recoil and let's you use a standard buffer and spring. AND if you already have an AR-15, you can use the endomag and just run 9mm in a regular ar15 lower. And the bolt holds back.
 
greyling, if you don't mind, I'm gonna IM you with some questions. That radial delay system has me really interested. I haven't shot one yet, but I'm hearing it's the next best thing to gas operated.

I agree, the Scorpion wasn't anything special. I shot one last week and wasn't impressed.
 
TonyAngel said:
greyling, if you don't mind, I'm gonna IM you with some questions. That radial delay system has me really interested. I haven't shot one yet, but I'm hearing it's the next best thing to gas operated.

I agree, the Scorpion wasn't anything special. I shot one last week and wasn't impressed.
Click to expand...

The scorpion is a cheap gun that has an expensive price tag. It works, and if it was $400 it would be amazing. The gen 3 finally corrected some of the glaring issues with it, but I always felt it was a prototype gun that somehow got put into full production.
 
Has anyone shot the Grand Power Stribog? I've seen them sometimes at very attractive prices.

John
 
I built a CMMG banshee as well but I could never get it to work reliably. Always had failures to eject. I finally had enough of it and bought back the first AR9 I had before that, from the person I sold it to. I got a Scheel Manufacturing roller delayed buffer to try with that.
 
With regard to barrel length, I can understand going longer for velocity reasons, but also consider what you might want to do with it. I built mine around a 5.5" barrel to keep it small. 9mm is a round that begs to be suppressed and with a short barrel and suppressor it's still pretty small. Longer than 5.5" or so and when you add a suppressor it starts to get to be a whole lotta gun for what it is.

Personally, if I wanted a long barreled .35 cal, I'd start thinking 350 legend and get the real oomph.
 
My thinking is, that if I have a full sized carbine, it might as well shoot a real caliber. If I have a platform that's larger than a usual service pistol, I at least want some additional barrel length, so it will hit harder.

That leads me to the 8-12" barrel range for something like a 9mm.
 
DMW1116 said:
Building an AR9 ... pistol or 9mm carbine for my son. I’m was thinking we could make it a project.
Click to expand...
Sounds like fun project to do with your son. :):thumbup:

DMW1116 said:
I plan to check PSA later today. They have a retail store near my office. I also have a local cohort who’s built 4 AR9s so I’ll talk to him too.
Click to expand...
Good plan. I have been happy with my PSA builds, including AR9s.

I have gone the way from using magwell blocks/Colt pattern 9mm stick magazines to Just Right 9mm with 40S&W/45ACP conversion kits to dedicated Glock lower AR9s and even EndoMag with regular AR lowers.

Since other members covered the LRBHO (Last Round Bolt Hold Open) question, I will focus on the basic build issues I have learned/resolved during my builds:
  • Dedicated magazine lowers like Glock which I recommend came to being as using magwell blocks to insert in ARs for Colt pattern stick magazines experienced feeding reliability issues. I use Frontier Armory Glock lower which builds many other brand Glock lowers (I bought Joe Bob Outfitters) and rounds are angled and positioned to essentially be pushed straight into the chamber for almost no "bumping the feed ramp" insertion reliability (And Glock compatible magazines like MagPul, KCI and ETS are cheap and readily available ... I have used factory Glock and MagPul magazines with 99.9% reliability).
  • For range plinking fun shooting, I don't think LRBHO is essential but if cost difference is not that much, why not.
  • For same manual of arms shooting drills with my ARs, I use CMMG 22LR conversion bolt kits and while not as accurate as dedicated 22LR rifles, accurate enough for 25-50 yard plinking fun at much lower shooting cost over .223/9mm.
  • Now days, "hybrid" bolts that are compatible with Colt and Glock pattern magazines are common place and should work with just about any upper.
  • With carbine recoil spring, 19-22 oz combined weight of bolt and buffer produces more comfortable felt recoil and will keep the front sight more steady on the target. (16-18 oz combined weight produces harsher felt recoil and will make the front sight dance around more). My PSA hybrid bolt weighs 14.7 oz and PSA buffer weighs 5.3 oz for 20 oz combined weight and produces comfortable felt recoil with various 100/115/124 gr 9mm loads.
If you are looking to shoot matches/competition or want a flat shooting AR9 with more steady front sight on target for faster follow up shots, check out this post on different bolt types - https://www.thehighroad.org/index.php?threads/9mm-pcc-bolt-choice.903452/#post-12248344

Have fun with your son.

TonyAngel said:
That radial delay system has me really interested. I haven't shot one yet, but I'm hearing it's the next best thing to gas operated.
Click to expand...
If you haven't, check out the well tested delayed TACCOM 3 stage recoil system and their new air cushion system (with claim of faster reset) and note how flat muzzle stays (Scroll down to "Delayed Blowback" section of post) - https://www.thehighroad.org/index.php?threads/9mm-pcc-bolt-choice.903452/#post-12248344


 
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DMW1116 said:
I’m already looking for loads to push past 1500 fps.
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If you shoot further than 25 yards, bullet drop can factor in starting at 50 yards and definitely show at 75-100 yards of several inches and more.

After getting shotgun pattern at 75-100 yards with 124 gr loads, I tested lighter and faster 115 and then 100 gr 9mm loads pushing around 1500 fps for more flatter shooting and smaller group testing. BTW, these are my 100/115/124 gr test loads and chrono data shot with PSA and JR carbine - https://www.thehighroad.org/index.p...n-9mm-40s-w-45acp.799231/page-4#post-10338994
  • 100 gr RMR HM RN 4.5-4.7 gr Promo @ 1.050": 1478-1475-1480-1471-1467 fps (58 F - JR carbine)
  • 100 gr RMR HM RN 5.5 gr W231/HP-38 @ 1.050": 1493-1468-1432-1479-1454 fps (58 F - JR carbine)
I found with blowback action, faster burning powders expanded the case neck and sealed with chamber wall better before bolt/buffer started moving back and lighter 100 gr bullet pushed to near 1500 fps with faster burning Promo/W231/HP-38 produced smallest groups of 1.5"-2" at 50 yards and 3.5" at 100 yards.

index.php

index.php


My testing with even lighter 95 gr FMJ produced down to around 1" groups at 45 yards (Shooting area was packed and that was best I could do that day) - https://www.thehighroad.org/index.php?threads/9mm-pcc-handloads.894850/#post-12054942

index.php
 
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JShirley said:
That leads me to the 8-12" barrel range for something like a 9mm.
Click to expand...
Consider shorter vs longer barrel for accuracy - https://www.thehighroad.org/index.p...most-accurate-9mm.906663/page-4#post-12324744
 
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