What do I need to build a AR 9 ?

[dangerranger60]

I have a complete lower that I have not done anything with for several years. I'm thinking of building an AR 9 from it but know next to nothing about them. I need an upper but some are described as side loaders? I need a recoil spring where the gas piston used to be. I need a mag block adapter and with that choose what mags to use And I see some discussion about ejector and last shot bolt hold open. [I'm also going to build featureless for use in CA But I think I have that sorted].
What am I missing? What do I need to know about the mag block and mag type. Are the Glock style mags better , more reliable, or cheaper? or is Colt style mags the way to go?
This is going to be a 16" rifle. A range toy, and a gun my wife could shoot, If she wanted. I also want to try some type of Red Dot sight. Having never used one would you go with a reflex sight or a optic type?
Thanks in advance for any help, DR

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[Alexx1401]

I have a couple and LOVE them. I used lowers that were made for the AR9. Then built them with simple parts kits and a factory upper all ready to go. Last one I made I used a Foxtrot Mike upper. If the lower is made for .223 556? you will need and adapter. I have one made by Stern that I still have not had time to play with. They are said to be top of the line. They are costly though. Paid about $200 for the one I have IIRC. There are some cheaper ways to go but I wanted something reliable.

 

[Steel Head]

I also used a dedicated 9mm lower
With regular lowers modified mags or magazine well adapter is needed.
Then you just need a 9mm barrel, bolt and buffer
You can get a special long buffer, plug or stack of quarters to limit bolt travel

I really enjoy shooting mine.

 

[dangerranger60]

I'm hoping for a reliable gun also. I see some of the mag adapters have an ejector in them and others that don't, What determines if I need that or not? Also what type of mags do your guns use? and are you happy with them? Thanks DR

 

[Steel Head]

I use glock mags
My build has been perfectly reliable even with hollow points.

I'd think an adapter without en ejector must be used with a bolt with an ejector in it.

 

[Alexx1401]

The Stern I have has the ejector with it. Far as I know you do need one. My dedicated AR9 lowers came with one already on them and on one it broke one day. The rifle would no longer work and took me a few to see what had happened. So with a lower not made for the AR9 the adapter would have to have one.

 

[dangerranger60]

I use glock mags
My build has been perfectly reliable even with hollow points.

I'd think an adapter without en ejector must be used with a bolt with an ejector in it.

Thanks, So the upper will tell me if I need it or not. Thanks again DR

 

[Alexx1401]

I'm hoping for a reliable gun also. I see some of the mag adapters have an ejector in them and others that don't, What determines if I need that or not? Also what type of mags do your guns use? and are you happy with them? Thanks DR

Both of mine have been reliable enough I would have no trouble trusting them for defense. Both are set up for Glock as I already had several PCC's that use Glock so I wanted them all the same. I have been "told" the set up using Colt type mags is easier to make reliable but have no idea if this is really true or not since I have had no problems with mine other than the one time the ejector snapped off on one.

 

[Steel Head]

Thanks, So the upper will tell me if I need it or not. Thanks again DR

Really it's the lower or bolt that dictates the ejector

Look at the Aero upper receiver with the last round bolt hold open as well
It pretty nice.

 

[Steel Head]

 

[dangerranger60]

View attachment 1213853

So this one used a reflex sight? How well do you like it? Are there any down sides?
Also this one uses the original charging handle, so it would be a smooth sided upper? Thanks for posting, and answering my questions. DR

 

[Member 34319]

Builds based off regular AR lowers are just as reliable as dedicated pistol caliber lowers.

Stern Defense makes adapters for many versions of pistol magazines. These include an ejector. Most if not all magazine adapters include an ejector. Ejectors are also built into dedicated pistol cal lowers. If you are going to use your AR15 lower the stern adapter is all you need in terms of an ejector.

SHOP STERN DEFENSE - MAGAZINE ADAPTERS - Stern Defense

getstern.com

Glock magazines are very popular, available, and there are very reliable and inexpensive copies out there. But if you have a lot of a certain pistol magazine, just look for an adapter for those magazines.

Global Ordnance Magazine Glock type 33rd 9MM Black UPC: 850003223063

Global Ordnance

globalordnance.com

Uppers can be bought outright or pieced together. It's usually 3 pieces vs many if put together, barrel bolt and handguard. Most uppers work with mag well adapters, so buying a completed one is about as easy as it gets.

Pistol caliber ARs are a fine firearms and have lots of uses, you'll enjoy having one.

 

[Pandaz3]

Really I think it best to make a 6,5, 6.8 or 300 blackout with your lower existing receiver. For an AR-9 use dedicated 9 MM receivers as they mate at proper anbgles with magazine in proper location to the chamber. I have two Angstadt which is a little delicate, but very refined, or PSA, rough , rugged, no nonsense, less expensive. Both mine are 10.5" pistols, a 16" would have a good bit more velocity, but I have fired to 100 yards accurately with mine, no opportunity to shoot further so I don't know more than what I have done.

AR-9's are blowback, not gas-impingement or piston actuation.so they have a proprietary bolt, no universal BCG.

 

[Pandaz3]

Aero Precision now builds quality AR-9 parts too.

 

[BrentN]

Aero Precision now builds quality AR-9 parts too.

+1. Recently completed an epc-9, super happy with it. Parts are quality, reasonable price, nice deal on mags, and so far, no hiccups. Had to wait a few weeks for the proprietary bolt to be in stock, and another few weeks on top of that for the charging handle, though a standard AR CH works fine.

 

[dangerranger60]

Really I think it best to make a 6,5, 6.8 or 300 blackout with your lower existing receiver. For an AR-9 use dedicated 9 MM receivers as they mate at proper anbgles with magazine in proper location to the chamber. I have two Angstadt which is a little delicate, but very refined, or PSA, rough , rugged, no nonsense, less expensive. Both mine are 10.5" pistols, a 16" would have a good bit more velocity, but I have fired to 100 yards accurately with mine, no opportunity to shoot further so I don't know more than what I have done.

AR-9's are blowback, not gas-impingement or piston actuation.so they have a proprietary bolt, no universal BCG.

100 yds is as far as I can shoot at home. So that's about as far as I need.

 

[Steel Head]

So this one used a reflex sight? How well do you like it? Are there any down sides?
Also this one uses the original charging handle, so it would be a smooth sided upper? Thanks for posting, and answering my questions. DR

I like it, fast and compact.
They aren't what I'd use for lots of outdoors use in nasty elements.



Yes! No side charger or extra stuck bolt button.

Aero Precision now builds quality AR-9 parts too.

Yep, they make nice stuff, the dedicated upper they make had a very well sized barrel register and fit very well on my PSA lower and having bolt hold open is nice.

 

[powermad]

If I was to build another AR9 I would would use the CMMG RDB.

Barrel and BCG Kit, 16" 4140CM, SBN, 9mm | CMMG - AR 15 and AR 10 Builds and Parts

The CMMG® 16” 9mm Barrel and BCG Kit allow you to build a Pistol Caliber Carbine using our Patent Pending Radi

cmmg.com

You can use either their Pmag inserts like the Endomags I had or an adapter for pistol mags.
That system will let you use a carbine spring and buffer and they have carrier tuning weight kits.

If you are going to go with a regular blowback upper you will need a different spring and buffer.
Vltor now makes PCC buffers and has an action kit with more buffer weights up to 10 oz if needed.
The one supplied in the kit should bring the total reciprocating mass to around 22 oz which is a good starting point.
https://www.vltor.com/shop/ar/buffer-components/sp-pcc-a5-pcc-spring-and-buffer-kit/

I would use a PCC hammer, some don't have problems with a regular one and some do.

NEW Enhanced PCC Hammer

Centurion Arms, with our team of combat experts have created the best weaponry for sale. Made for and trusted by SEALs, we take great pride in our products.

centurionarms.com

Or trigger pack like the CMC PCC trigger.

I used a KVP BCG

KVP 9MM Blow Back Bolt Carrier Group - Kaw Valley Precision

The KVP 9mm BCG is a feature packed solution for your 9mm Blow Back Carbine or Pistol. Our 9mm BCG is compatible with either Glock or Colt style magazines. The carrier is constructed of US made 8620 steel, with a Nitride QPQ finish.

kawvalleyprecision.com

 

[USMC1911]

I have found both the Frontier Armory receiver set and the Areo Precision receiver set to be good starting points. I really like the side charge Frontier setup out of the two.

 

[arakboss]

A lot of patience.