Ar9 build

[Cameramonkey]

I have several builds. Both dedicated Glock billet lowers and drop in mag blocks. Functionally I cant tell the difference between my standard AR with a KAK Colt pattern mag block and my Glock fed dedicated lower. They all function flawlessly.

The only questionable thing was the Glock lower with a specialized LRBHO upper. That was a hot mess that relied HEAVILY on the mag spring strength to function reliably. Other than that nuanced build I cant say anything bad about my others.

 

[ROLEXrifleman]

As has been stated, the 9mm AR is a highly temperamental build since it is blowback operated. One thing not specifically mentioned but is of worth to point out is Out Of Battery Detonation.
I don’t care if it’s a factory build or a home brew. One thing that has to be addressed is the type and weight of the buffer. If you’re not sure what buffer weight and type, solid vs reciprocating, has to do with the build you should do a lot more homework. Depending on the parts in play and the speed at which the trigger is pulled, an Out Of Battery Detonation is very likely at some point. Even factory builds are prone to it.
In addition, the bolt style, being ramped or unramped effect what hammer can be used . Do you're homework thoroughly on this one. A blowback 9mm ar can bite you hard if it’s done wrong.

 

[bwframe]

As has been stated, the 9mm AR is a highly temperamental build since it is blowback operated. One thing not specifically mentioned but is of worth to point out is Out Of Battery Detonation.
I don’t care if it’s a factory build or a home brew. One thing that has to be addressed is the type and weight of the buffer. If you’re not sure what buffer weight and type, solid vs reciprocating, has to do with the build you should do a lot more homework. Depending on the parts in play and the speed at which the trigger is pulled, an Out Of Battery Detonation is very likely at some point. Even factory builds are prone to it.
In addition, the bolt style, being ramped or unramped effect what hammer can be used . Do you're homework thoroughly on this one. A blowback 9mm ar can bite you hard if it’s done wrong.

I had this happen "right in my face" at a steel match that I was RO'ing. Happened in a factory JP Rifle PCC, none the less. The gun had malfed the stage before, but showed no signs of problems. Next stage, boom. The gun got bagged for the rest of the match.


- A wake up call for a lot of folks with "completely reliable" AR9's is to run them hot and fast in a season of competitive shooting matches.

A few years back, when AR9's were newer, one of our early INGO'ers convinced Pat Rogers to let him come to a rifle class with his AR9. He assured Pat that his AR9 was well tested and reliable. Pat reluctantly allowed the gent to come, saying "Your gun better run..." IIRC, the man finished Pat's class with a classmate's backup 5.56 rifle.

 

[ROLEXrifleman]

Thank you for sharing that experience. Just proves my point even “top tier” rifles are prone to the syndrome.
In an AR9, if it’s to be run “fast” it needs to be built to submachine gun specs. That being a 9mm two piece reciprocating mass buffer with a spacer, not the one piece extended heavy mass units.

Semi guns with aftermarket short reset, or “enhanced” triggers are even more susceptible. Hell, anyone running a milspec trigger can make it go boom. At the end of the day people really need to do their research on these. Everyone loves picking up a 20+ round stick and go as fast as they can, it’s a recipe for disaster. The other scary part is that PCC are used so often to “teach” children, new shooters and women..... hell of an experience when they get an explosion in the face cause the “teacher” doesn’t know what he has going on.
Be careful is my point, I guess.

 

[92FSTech]

I had a PSA blowback 9mm AR that was nothing but trouble. Doubling and out of battery discharges. I tried all kinds of spring and buffer options to correct it, finally just ended up getting rid of it.

I now have a CMMG Radially-delayed blowback gun that has been working very well. None of the issues that I had with the straight blowback rifle, and it's much softer shooting. It also has LRBHO that works very well, and runs off a standard lower using the pmag endomag conversions.

It did eat an ejector pin after about 1000 rounds...seems like the action is battering that part pretty good, and I've seen other reports of the same online. Thankfully it's a pretty easy and inexpensive fix. I replaced it and CMMG sent me some spares for free, as well as weights to tune the BCG. I haven't had a chance to put many rounds through it since I fixed it...just enough to verify function...but so far so good.

 

[Indy574]

Ran across this on AR15.COM. Thought it was worth posting.

Blowback9.com

No-BS information for the 9mm AR.

blowback9.wordpress.com

 

[Nickbau5]

A bit late to the conversation, but on the topic of Upper and Lower, my AR9 is built on a New Frontier Armory for both, I personally like their design since the lower is made for glock mags, and the upper is a simple sleek design. The lower is nice quality, no need for roll pins as the places that you would normally have to struggle with are replaced with little hex screws and it's a solid trigger guard. The Upper is also really nice, and is specifically made to allow for a LRBHO.

Overall I think those 2 are great choices for a build albeit a bit more pricey than other options. Here's my good ol girl I build a couple years ago.

 

[mcapo]

Not to talk you out of a build. With careful parts selection, proper compatibility can result in reliability.

but

If you decide otherwise, here is a great Indiana manufacturer.

FX-9 - Freedom Ordnance

FX-9 BUILD IT EXACTLY LIKE YOU WANT IT. BUY NOW Three barrel lengths. Modular design that is AR-15 configured and compatible lets you create the exact build for your next mission. One-hundred percent made in the USA. This is freedom to the extreme. LET FREEDOM REIGN FEATURES01 FEATURES FORM AND...

freedomordnance.com

 

[ed1838]

i used a new frontier lower that takes glock mags on my build. So far no problems only 100 or so rounds thru it. On mine I do not have last round bolt hold open. Would like to have it. Was thinking about a way to do it.

 

[Nickbau5]

i used a new frontier lower that takes glock mags on my build. So far no problems only 100 or so rounds thru it. On mine I do not have last round bolt hold open. Would like to have it. Was thinking about a way to do it.

To have it you need the upper that has it, so the NFA upper is one of the few that does

 

[ed1838]

To have it you need the upper that has it, so the NFA upper is one of the few that does

i used the NF lower but a different upper I think fox trot made a lower with some mods that had it made into the lower

 

[Nicu757]

QC10 has all you need for a AR9. Was my first build learned to get all the parts from the same place.

 

[Nicu757]

Mines a SBR but a brace works just the same

 

[Refrigerator27]

Mpx are just to much for me. The scorpion is ok but not really helpful when trying to learn the setup of building. Cmmg was the other interesting one I saw but again was looking to break into the ar style market with ammo I already have available as prices are still high from what I see

Look into the Ruger PC Charger in 9mm pistol format. Barrel can be taken down and takes glock mags. I've been eyeing it for some time now.

 

[crosse]

I can tell you that trying to cheap out on parts (quarters in the buffer tube) or cheap bolts/barrels will lead to issues most likely. I tried at least 4 different buffer setups (spring/buffer) before taking advice from the manufacturer and using a 308 spring with a true 9mm buffer and a quality well known bolt from new frontier and barrel from Ballistic Advantage. I don't recommend any parts from Spinta Precision (they're probably out of business now). But I ended selling that build and going with a FM products lower CMMG banshee build.