AR9 build info

Mr_Roboto

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[MENTION=249]importcrew[/MENTION] can probably speak up a bit on this more, but [MENTION=7435]BADAZZTEALCOBRA[/MENTION] requested some info on AR9 building. Here's kind of a combination of my research and what's worked for me.

-There's a few options for bolts and hammers. If you use a non-ramped bolt you'll need a notched hammer or something aftermarket that's compatible. My advice is certainly to get a ramped bolt. You don't really spend any more bank on it tbh.
-The bolt needs to be set up for the mags you use. If you use double stack that's any bolt option. If it's single stack you need a compatible bolt.
-Barrel wise I went with an M4 style barrel. I want the match style barrel in retrospect, less weight.
-Threads for muzzle stuff is 1/2-36 which is an oddball thread. Prepare to spend bucks on something for this. The thread protector I got was off ebay and the cheapest I found. Want to trim to 13" or so and permanently attach a flash can.
-Low Receiver wise there's a few options. You can get a standard lower and use a block (some go in the top, some go in the bottom more on this below) or you can get a dedicated lower. Colt (modified Uzi mags) MP5 mags (appear to be a thing now) M&P mags and the ubiquitous Glock mags are all options I've seen at some point or another.
-Mag blocks there's a lot out out there. Heard good things about the Hahn ones, (at $200 they'd better be good) I actually use the cheapie Promag block. Everyone hates on Promag but mine works great with ASC Colt magazines and is about 50 bucks. I got mine on cheaper than dirt for about $13 each on sale, but you have to watch.) I modified mine by drilling a hole in the front of the lower then threading it and using a set screw. This lets me pull the block out the bottom. Last shot hold open even works!
-If you use a top feed block the bolt catch has to come out, at least with the Promag block. I don't know about with other stuff.
-Get more buffer weight. It makes the gun a lot more pleasant to shoot. I have about 7 quarters behind my standard AR buffer, and I have the extra weight in the bolt too. I'd get a heavy buffer if I was you. I broke a bolt catch before this and the gun was not nearly as nice shooting.
-There's an ejection port cover that's got a brass deflector built in. CMMG and Colt both make em. I've used both, and they're a nice upgrade. Also work great on 22LR ARs as well.
-Some people say these do have problems with bolt/hammer pins. I've used 80% on RRA National Match triggers and rack style triggers without issue. My G2S wasn't as good at pin retention, so I ended up with KNS pins.
-I spent a few more bucks and got a slick side upper. Not required but I didn't want the weight of the FA and added space on the upper. Would spend again.
-Handguard wise, a standard handguard will work. I use the same one I use on my 5.56 gun just to have parity.

Really that's about what there is different. All standard AR tools work. You don't need a gas block or tube and most of the rest of the parts are standard AR.
 

BADAZZTEALCOBRA

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Okay, so here are my thoughts on the build, and Im likely way off base so hopefully I dont make too big an ass out of myself on it. :bowrofl:


-I want it to be Glock magazine compatible. All my handguns are Glock so might as well stick with the magazine since it's what I have laying around.



-I want it to be a pistol so was thinking of the Maxim Defense pistol brace with the 9mm JP SCS buffer weight and spring setup.



-I was thinking somewhere around an 8" length of barrel at the most, but need to research this more. Is there an ideal length of barrel for a 9mm pistol build?


-I would also like to stick with a flat face CMC Trigger on this build since it's what I use on my AR builds.




Is there a different barrel nut and all that on an AR9 upper? Of if I buy any AR handguard, will I be able to use their barrel nut setup on the AR9 upper?
 

1MEANGT

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I built my own AR9 pistol a year or 2 ago.

Used a dedicated PSA AR9 lower that accepts glock mags. I also installed a G2S trigger with no issues.

Used a standard AR stripped upper with a 10.5" barrel and bolt through PSA.

Using the shockwave blade for the pistol brace.

It is a blast to shoot. If I remember correctly the only thing that does not operate like a regular AR is it will not hold the bolt open after the last round. But the bolt stop does hold the bolt open manually.
 

1MEANGT

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Is there a different barrel nut and all that on an AR9 upper? Of if I buy any AR handguard, will I be able to use their barrel nut setup on the AR9 upper?
The barrel nut that comes with whatever handguard you choose should work. At lease it did on my build and I used a BCM handguard.
 

Mr_Roboto

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-Glock dedicated lower then, get a ramped single stack bolt and you're good to go
-ballistics by the inch shows ~13" being max you really wanna beat with an AR9. 16" is strictly for rifle compliance on my part and you're not going to get a huge penalty going shorter.
-use what trigger you want with the above bolt. Any standard one will work.
-JP makes a 9mm version. I wouldn't use a 5.56 version at all. It says weight removal required. I use a standard buffer tube so I don't see an issue with whatever you use short of it being a PDW style stock that uses a customized bolt.
-Use a standard nut. and handguard. No differences.
 

BADAZZTEALCOBRA

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If I remember correctly the only thing that does not operate like a regular AR is it will not hold the bolt open after the last round.

I was just reading that the PSA lower does not, but some of the other lowers that cost a little more do....


I figure I might as well put some of the "extras" I have laying around for AR builds to use. :bowrofl:
 

Shawn1112

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What should one expect to spend to build something decent?
Kind of like where badazztealcobra is going with his build.
So something similar to his build would cost what, ballpark figure is fine.
 

BADAZZTEALCOBRA

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What should one expect to spend to build something decent?
Kind of like where badazztealcobra is going with his build.
So something similar to his build would cost what, ballpark figure is fine.

I tend to get stupid on these things so Im not the one to ask.... HAHA


Im betting you can do one cheap from PSA for sure, but I'm not planning on that for this build.



Hell, the brace setup alone is $500.


https://www.rainierarms.com/maxim-defense-cqb-pistol-pdw-brace-for-ar15-black/



Cause Im a moron. :bowrofl:
 

Mr_Roboto

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What should one expect to spend to build something decent?
Kind of like where badazztealcobra is going with his build.
So something similar to his build would cost what, ballpark figure is fine.
The prices are roughly the same as standard AR parts honestly. The lower's more expensive for a dedicated (under 200 typically) or 50-200 for a mag bloc and I paid probably 30-40 more for a slick side upper, and then another 10 or so for the specialty deflector/ejection door. You don't need a gas block or tube unless it's your front sight.

The mags are probably the catch. I think you'd save money in the long run if you had Glock mags already and ran them, or even getting an AR9 lower for Glock mags if you aren't planning on going back and forth like I set mine up to.

I love mine, I take it to indoor ranges that don't allow rifle calibers. It's quiet too. I usually shoot home cast 9mm (see reloading thread and I am at $3-3.50 a box for doing it. Can't complain at all.
 

BADAZZTEALCOBRA

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Just priced it out on a spreadsheet and came up with $2700 including the optic.


I went a little stupid with it though and I'm betting you could cut that in half if you wanted to easily.
 

cobravenom39

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I built my own AR9 pistol a year or 2 ago.

Used a dedicated PSA AR9 lower that accepts glock mags. I also installed a G2S trigger with no issues.

Used a standard AR stripped upper with a 10.5" barrel and bolt through PSA.

Using the shockwave blade for the pistol brace.

It is a blast to shoot. If I remember correctly the only thing that does not operate like a regular AR is it will not hold the bolt open after the last round. But the bolt stop does hold the bolt open manually.
Pretty much the same thing, here. I originally had a shockwave blade, but replaced it with a standard buffer tube / receiver extension and went SBA3. Game changer.
 

cobravenom39

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Just priced it out on a spreadsheet and came up with $2700 including the optic.


I went a little stupid with it though and I'm betting you could cut that in half if you wanted to easily.
You have to stop making spreadsheets with the costs. That's the work of the devil.
 

BADAZZTEALCOBRA

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Pretty much the same thing, here. I originally had a shockwave blade, but replaced it with a standard buffer tube / receiver extension and went SBA3. Game changer.

I have an SBA3 on the 300BLK pistol, definitely nice, wanted to try something different when I eventually build the PCC though, my focus now is on a G34 build that Im in the middle of...


You have to stop making spreadsheets with the costs. That's the work of the devil.

I just like to have a ballpark figure on things, it doesnt deter me from buying the stuff, otherwise I wouldnt have ever built my lightweight AR. :bowrofl:
 

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