9mm AR pistol, adaption or purpose built?

[gun'sRgood]

I have come around to really liking the concept of an AR 9mm. There seems to be two basic choices. Adapt an AR 15 to shoot 9's or get a purpose built AR 9. Other than you can switch an adapted AR back and forth, I'm not sure of the pro's & con's. Is there, or are there certain companies that are well worth looking into? And the same for companies that I should stay away from? Same for companies who build the AR 9's. Who's got the top and who's got the bottom. I would guess that by now all the top rated gun companies have top rated 9's? Or are their start-ups I'm not seeing?

 

[NIGHTLORD40K]

I built one using the Stern Defense magwell adapter-

This particular one is for Beretta M92 magazines, but of course they also make models for Glock and Colt SMG mags. On the plus side, it is VERY well made and engineered, and incorperates a last round bolt hold open. Reliability has been 99% and the few problems have been due to the standard .223 ejection port being a hair narrow. On rare occasions 9mm brass will get stuck at a 90deg. angle in the port.

It is not really a "quick-change" proposition, however, as you do have to tighten 2 set screws at the bottom to tension the adapter against the original mag release. Also, because it uses its own mag release at the bottom, pushing forward, it requires different muscle memory to change mags.

Its also quite $$$.

I also have a PSA PX9 purpose-built 9mm carbine which uses a dedicated Glock-mag lower and upper with an enlarged ejection port. Function has been 100% so far and the complete gun cost significantly less than the conversion build. All the controls are identical to a standard AR (though not ambidextrous). My only minor gripe is that it does not hold the bolt open on an empty mag.

If I were to do it again, I would just get a purpose-built 9mm gun or at least dedicated 9mm upper and lowers to build my own.

 

[berettaprofessor]

I bought a Foxtrot Mike 9 mm/Glock mags and love it; greatest plinking tool on the planet, after a S&W MP 15-22 of course. However, I'm already wondering about it since it came with a SB3 brace which may not be legal soon.

 

[Rembrandt]

Several good dedicated units out there, CMMG Banshee, Wilson Combat AR9G are quality pieces. Went with the Foxtrot Mike FM-9, less money and top workmanship. Pleasant to shoot when suppressed.

 

[12Bravo20]

When I built my AR9 pistol, I ended up going with a dedicated Colt style lower. I personally just like the looks of the Colt style magazines over any other type. And the Metalform magazines have been 100% reliable for me. I used all CMMG parts except for the barrel and upper receiver. The barrel is a 10.5" 9mm barrel with A2 front sight post from Rock River Armory and the upper receiver is a 604 type slick side from Fulton Armory.

On what magazine style to go with, it depends on what you prefer or have more of on hand. A mag block adaptor makes sense if it is your only AR or you want to use other uppers on the lower receiver.

No matter if you go with a Colt style or a Glock style, make sure to get at least a 5.5 ounce carbine buffer. 5.5 ounces is the minimum weight for the buffer on 9mm AR's. I also suggest getting either a spacer to go behind the buffer or getting an extended buffer so you don't take a chance of breaking the bolt hold open lever.

 

[NIGHTLORD40K]

Several good dedicated units out there, CMMG Banshee, Wilson Combat AR9G are quality pieces. Went with the Foxtrot Mike FM-9, less money and top workmanship. Pleasant to shoot when suppressed.

View attachment 1004717

Nice! What buffer are you running with that setup?

 

[Rembrandt]

Nice! What buffer are you running with that setup?

Using a 6oz buffer and AR10 Carbine spring. Foxtrot Mike recommends 6.5oz buffer but was unable to find anyone that had them in stock. So far the 6oz is working flawlessly.

All the magazines are Glock or Magpul....work perfect.

 

[GunnyUSMC]

I’ve built a few of them using lowers made to take Glock mage. My favorite lowers are the Jo Bob Outfitters Spartan. They are made by New Frontier Armory.

 

[mjsdwash]

I use a magwell from Midway. The advantage of a normal receiver is that if you get bored with it, your not stuck, they look better, ergonomics are the same, and the controls. The other big advantage, its hard to find Colt pattern lowers, but easy to find the blocks. Some say the Glock pattern is better, but I don't agree.
The Colt pattern uses cheaper mags, at least for a given quality, and most people don't already have Glock18 mags lying around. I also hear far more "it doesn't work" stories with Glock pattern, and the Glock pattern has more aftermarket fixes.

Style is the biggest determiner for standard lower, or magblock.

I put a $60 magblock in a $40 PSA lower. I used a RRA barrel, and its good. I used a KAK bolt, and buffer. Its a 5.5oz tungsten (not solid) buffer with an AR10 spring. I uses Metalform and ASC mags, metalforms were around $24, and ASC were $12-18.... both were available all last year when everything was sold out.

I have about 2500 rounds through it, after approximately 1 year. It has issues with OAL of ammo, but loading shorter, about 1.140 or less, I have had no malfunctions that I can recall.

 

[Olympus]

If I were doing a 9mm build, I would certainly want to go purpose-built lower. As for the pistol, with all the new ATF Worksheet 4999 business, I would advise holding off or going dedicated SBR route with an actual stock. It's not going to be good for braces for the next 4 to 8 years, possibly longer.

 

[bullseye308]

I went the easy route and bought one complete from Palmetto State. 8” AR-9 fed from Glock mags. Runs like a top and I usually put ~400 rounds per range trip through it with no malfunctions. Close to 6k rounds so far and 2 hang ups that were ammo related. Everyone loves shooting it and it is just so much fun.

 

[gun'sRgood]

I built one using the Stern Defense magwell adapter-
View attachment 1004676
This particular one is for Beretta M92 magazines, but of course they also make models for Glock and Colt SMG mags. On the plus side, it is VERY well made and engineered, and incorperates a last round bolt hold open. Reliability has been 99% and the few problems have been due to the standard .223 ejection port being a hair narrow. On rare occasions 9mm brass will get stuck at a 90deg. angle in the port.

It is not really a "quick-change" proposition, however, as you do have to tighten 2 set screws at the bottom to tension the adapter against the original mag release. Also, because it uses its own mag release at the bottom, pushing forward, it requires different muscle memory to change mags.

Its also quite $$$.

I also have a PSA PX9 purpose-built 9mm carbine which uses a dedicated Glock-mag lower and upper with an enlarged ejection port. Function has been 100% so far and the complete gun cost significantly less than the conversion build. All the controls are identical to a standard AR (though not ambidextrous). My only minor gripe is that it does not hold the bolt open on an empty mag.

If I were to do it again, I would just get a purpose-built 9mm gun or at least dedicated 9mm upper and lowers to build my own.

I also went with Stern. It was the release, as you first mentioned, that got me thinking. Then I saw a few purpose built 9's and got that itch of I wanna own one! Thanks

If I were doing a 9mm build, I would certainly want to go purpose-built lower. As for the pistol, with all the new ATF Worksheet 4999 business, I would advise holding off or going dedicated SBR route with an actual stock. It's not going to be good for braces for the next 4 to 8 years, possibly longer.

I got what your saying. But I do think a whole bunch of bump stock just magickly reappeared.

 

[12Bravo20]

I forgot to post a photo of my Colt style build.

 

[doubleh]

My favorite son-in-law, only one I have so he gets the honor, bought a CMMG and I have shot it a little. This is a very nice gun and very accurate. If I were interested in this type of AR I would rate this right at the top of my list to consider.

 

[Mot45acp]

Foxtrot Mike's quality and service is 2nd to none. Owner emailed me back late on a weekend. I stripped out some screws (my fault) trying to change handguard and barrel. The gist of his email: "send me your parts and I will take care of it"

Less than a week shipping from Texas to Idaho and back. He remembered I was mounting a suppressor, so he swapped out the handguard for free. Gave me my old handguard and barrel back, assembled everything and it runs like a top. It did before, just wanted threaded barrel instead of tri-lug.

They have a proprietary thread locker compound that will not budge. I knew this and tried to remove it on my own. I admitted fault and they still squared me away. I heard that even if you are using competitor parts with theirs, they will still put it together. All it cost me was shipping to them.

 

[herrwalther]

I would opt for purpose built as opposed to getting a 9mm upper with conversion parts for a standard lower. By the time you dump money into converting a standard AR into a 9mm PCC AR, you are pretty much even cost of a dedicated build anyway. Going off pre-pandemic prices.