AR-9 Build Questions

[campinginaz]

I'm new to the site and although I have been around firearms all of my life I have never built one. I'd really like to buy or build an AR-9. I'm leaning towards building if it is not too complex. I haven't bought anything yet as I have been doing a lot of research. I want this for home defense so it must be extremely reliable. I have a PSA AR-9 and it is reliable but it does not have a last round bolt hold open and I really want that feature.

Here is what I have been thinking so far.

Dedicated 9mm lower
Takes Glock magazines
Last round bolt hold open
Needs to be very reliable and eat hollow points

As far as the components I was thinking of Aero Precision EPC-9 upper and lower set. Aero barrels on the other hand don't work well with hollow points from what I have read. I'm thinking of going with a 7.5 to 8.5 inch barrel.

Does anyone know of any barrels that have a feed ramp and are reliable? I have looked into Macon Armory but they are sold out. Taccom also seems like a good brand but they don't have the barrel length that I am looking for.

Any thoughts on what brand of bolt? Buffer weight? Trigger?

Any advice is appreciated. I'm totally new on this. I'd like to keep the budget reasonable.

Would be nice to hear from people who have an AR-9 and/or have built one.

 

[Suck My Glock]

For me, the most reliable feeding 9mm AR mag system has been the EndoMag conversion of Magpul magazines. The feed ramp geometry is not a radical angle and is very gentle in delivering hollow-points to the chamber. The neat thing is that you can use a standard AR15 lower and no need to drill and pin a conversion feed block in the magwell to use Glock or Colt/Uzi mags.

 

[YNOTAZ]

I use dedicated 9mm lowers with Colt smg mags and clones. They work great, not as easy to find as Glock stuff but they're made for full auto smgs so they run.

 

[campinginaz]

For me, the most reliable feeding 9mm AR mag system has been the EndoMag conversion of Magpul magazines. The feed ramp geometry is not a radical angle and is very gentle in delivering hollow-points to the chamber. The neat thing is that you can use a standard AR15 lower and no need to drill and pin a conversion feed block in the magwell to use Glock or Colt/Uzi mags.

opplanet-mean-arms-restrictive-states-endomag-9mm-10-round-black-2101169-av-1.jpg

Thank you! I thought about going this route as I could use my AR-15 lower. It's good to know these actually work. I watched some videos and one person did a review on these and another brand. He said these were reliable but I still had some doubts lol. I debated it for a bit and decided it would be nice to have a dedicated AR-9.

If you don't mind me asking what are you using for your upper? Which barrel and bolt? Are you using the standard AR-15 buffer or something different?

 

[campinginaz]

I use dedicated 9mm lowers with Colt smg mags and clones. They work great, not as easy to find as Glock stuff but they're made for full auto smgs so they run.

That does sound pretty nice. I mainly want one that uses Glock mags since I can not only save money on mags but use the same mags as other guns I own.

 

[XJThrottle]

***** I HAVE NOT SHOT IT YET ******

But, I did a standard AR lower with a magwell conversion to use Glock mags. Considering I have P80 pistols and Glock mags, and zero Colt mags..this was an easy choice.

The main thing for me was being able to SBR the lower, then use it for whatever I wanted. What I didn't want was a 16" 9mm AR. I wasn't going to shame myself into a pistol brace. I'd sooner go to the town square dance with monkey pox on my face....

 

[YNOTAZ]

Makes sense, if you already own something that takes Glock stick mags, stick with them.

Having a gaggle of different stick mags that all look alike but fit different firearms is a huge pain in the A$$ unless you have unlimited space to lay things out.

 

[Suck My Glock]

For me, the most reliable feeding 9mm AR mag system has been the EndoMag conversion of Magpul magazines. The feed ramp geometry is not a radical angle and is very gentle in delivering hollow-points to the chamber. The neat thing is that you can use a standard AR15 lower and no need to drill and pin a conversion feed block in the magwell to use Glock or Colt/Uzi mags.

opplanet-mean-arms-restrictive-states-endomag-9mm-10-round-black-2101169-av-1.jpg

Thank you! I thought about going this route as I could use my AR-15 lower. It's good to know these actually work. I watched some videos and one person did a review on these and another brand. He said these were reliable but I still had some doubts lol. I debated it for a bit and decided it would be nice to have a dedicated AR-9.

If you don't mind me asking what are you using for your upper? Which barrel and bolt? Are you using the standard AR-15 buffer or something different?

Well, I went a route most others have not, and I built my own radial-delay CMMG Banshee from parts back in 2018 because it was cheaper than buying the whole pre-made weapon. I also wanted a short 5in. barrel to keep things compact and to utilize as large a diameter carbon fiber free-float tube as possible so as to also act as a shroud over a suppressor. At that time, CMMG sold just the barrel and bolt, and you had to come up with your own upper and other bits. CMMG advised that building one of their Banshees required a non-milspec upper, with larger ejection port dimensions, to ensure reliable ejection of 9mm cases. I can't recall now where I ordered mine from, but it was from some cheapo parts house, as I was trying to do this as cheaply as possible. Other than the CMMG Banshee bolt and barrel, nothing was high-end brand name components.

I went with the radial-delay system specifically because in researching AR-based 9mm systems I was aware of the stresses the plain blow-back guns were having difficulty with. The bolt velocities were breaking hammer pins and elongating hammer pin holes in receivers. Low bolt assembly mass was making use of suppressors problematic due to the risk of prolonged pressure dwell times rupturing cases as they began moving rearward while still under combustion pressures. Recoil spring and buffer weights, in an attempt to compensate for these things became a complicate game of mix and match. Some sort of locked or semi-locked bolt system would seem to solve all this, and the CMMG radial-delay system does that. I was able to use a standard carbine buffer and recoil spring from the my spare parts bin. Everything about the build was made easy because of the radial-delay system.

 

[campinginaz]

I use dedicated 9mm lowers with Colt smg mags and clones. They work great, not as easy to find as Glock stuff but they're made for full auto smgs so they run.

I'm also thinking a dedicated 9mm lower will be the way I go. Thank you for the advice!

 

[campinginaz]

***** I HAVE NOT SHOT IT YET ******

But, I did a standard AR lower with a magwell conversion to use Glock mags. Considering I have P80 pistols and Glock mags, and zero Colt mags..this was an easy choice.

The main thing for me was being able to SBR the lower, then use it for whatever I wanted. What I didn't want was a 16" 9mm AR. I wasn't going to shame myself into a pistol brace. I'd sooner go to the town square dance with monkey pox on my face....

Time to get out there and shoot it! I agree I don't want a 16 inch 9mm AR either. I'll probably do a pistol brace if they are still legal (I'm sure you have heard about the ATF's shenanigans), or I'll end up turning it into an SBR.

"I'd sooner go to the town square dance with monkey pox on my face...." I don't think my face can be any worse so I'm not worried about an arm brace LOL!

 

[campinginaz]

For me, the most reliable feeding 9mm AR mag system has been the EndoMag conversion of Magpul magazines. The feed ramp geometry is not a radical angle and is very gentle in delivering hollow-points to the chamber. The neat thing is that you can use a standard AR15 lower and no need to drill and pin a conversion feed block in the magwell to use Glock or Colt/Uzi mags.

opplanet-mean-arms-restrictive-states-endomag-9mm-10-round-black-2101169-av-1.jpg

Thank you! I thought about going this route as I could use my AR-15 lower. It's good to know these actually work. I watched some videos and one person did a review on these and another brand. He said these were reliable but I still had some doubts lol. I debated it for a bit and decided it would be nice to have a dedicated AR-9.

If you don't mind me asking what are you using for your upper? Which barrel and bolt? Are you using the standard AR-15 buffer or something different?

Well, I went a route most others have not, and I built my own radial-delay CMMG Banshee from parts back in 2018 because it was cheaper than buying the whole pre-made weapon. I also wanted a short 5in. barrel to keep things compact and to utilize as large a diameter carbon fiber free-float tube as possible so as to also act as a shroud over a suppressor. At that time, CMMG sold just the barrel and bolt, and you had to come up with your own upper and other bits. CMMG advised that building one of their Banshees required a non-milspec upper, with larger ejection port dimensions, to ensure reliable ejection of 9mm cases. I can't recall now where I ordered mine from, but it was from some cheapo parts house, as I was trying to do this as cheaply as possible. Other than the CMMG Banshee bolt and barrel, nothing was high-end brand name components.

I went with the radial-delay system specifically because in researching AR-based 9mm systems I was aware of the stresses the plain blow-back guns were having difficulty with. The bolt velocities were breaking hammer pins and elongating hammer pin holes in receivers. Low bolt assembly mass was making use of suppressors problematic due to the risk of prolonged pressure dwell times rupturing cases as they began moving rearward while still under combustion pressures. Recoil spring and buffer weights, in an attempt to compensate for these things became a complicate game of mix and match. Some sort of locked or semi-locked bolt system would seem to solve all this, and the CMMG radial-delay system does that. I was able to use a standard carbine buffer and recoil spring from the my spare parts bin. Everything about the build was made easy because of the radial-delay system.

Thank you so much for taking the time to write this response and provide pictures. Very nice looking build by the way! I had looked into the CMMG Banshee and they are just pretty expensive. I like your idea of buying the bolt and barrel and building one.

After looking at my PSA AR-9 it has a 4 inch barrel and it has the KAK flash can (which I will probably go with on my build). I don't have a 9mm suppressor but it's something to consider.

For your upper receiver did you get one that has a larger ejection port, or is yours a standard AR-15 upper? I'm wondering if I can use the CMMG barrel and bolt in an Aero upper receiver (so I have the last round bolt hold open feature). I might have to call the manufactures on that or do some more research. Essentially I could build an upper and use my PSA lower for now since the Aero upper is what has the LRBHO feature.

Have you shot hollow points through yours? How many rounds would you say you have put through it? How has it ran?

 

[campinginaz]

**Update** I went ahead and ordered the CMMG bolt and 5 inch barrel. Going to build around this. Next step will be an upper with an enlarged ejection port.

I'm checking with CMMG to see which CMMG model works as their website is a bit vague.

Anyone know if this will work as well?
https://www.aeroprecisionusa.com/ar15-xl-stripped-upper-receiver-fde-cerakote

**Update** checked with CMMG and this is the upper that will work with the enlarged ejection port in case anyone was wondering.

https://cmmg.com/upper-receiver-assembly-mk4-ar15

 

[Suck My Glock]

Sounds like you have researched this a little bit and are finding the answers. Good for you. Realize before you order the Endomag conversions that there are 2 different types; one specifically for the CMMG Radial-Delay system (which does not require and ejector in the mag), and the one for every other 9mm system (which requires an ejector protrusion in the mag conversion).

When I built mine in 2018, CMMG did NOT have a version that worked with Uzi/Colt mags. That was what I actually wanted to use, and I chose to go with the Endomags only as a temporary solution until I could somehow get the Uzi/Colt mags to work with the CMMG system. Today, due to popular demand, CMMG does indeed have the modified components to build a version that uses the Uzi/Colt mags. But I've been so satisfied with the Endos, I'm not switching.

 

[campinginaz]

Sounds like you have researched this a little bit and are finding the answers. Good for you. Realize before you order the Endomag conversions that there are 2 different types; one specifically for the CMMG Radial-Delay system (which does not require and ejector in the mag), and the one for every other 9mm system (which requires an ejector protrusion in the mag conversion).

When I built mine in 2018, CMMG did NOT have a version that worked with Uzi/Colt mags. That was what I actually wanted to use, and I chose to go with the Endomags only as a temporary solution until I could somehow get the Uzi/Colt mags to work with the CMMG system. Today, due to popular demand, CMMG does indeed have the modified components to build a version that uses the Uzi/Colt mags. But I've been so satisfied with the Endos, I'm not switching.

I definitely do a lot of research, it's half the fun I think! I definitely want to use Glock mags, so far I have ordered the CMMG bolt, barrel and upper receiver. Since the last round bolt hold open on the CMMG's is on the lower I'll probably look for one of these locally first.

https://cmmg.com/lower-receiver-assembly-mkgs-lower-receiver-mag-catch-bho-linkage

 

[shorepatrol]

Bought a PSA AR-V 8" 9mm this weekend after looking through this thread

 

[campinginaz]

Bought a PSA AR-V 8" 9mm this weekend after looking through this thread

Nice! Where did you buy it if I may ask?

 

[shorepatrol]

Bought a PSA AR-V 8" 9mm this weekend after looking through this thread

Nice! Where did you buy it if I may ask?

Straight from PSA. Blem was 699 with free shipping. It has the last round bolt hold open feature

 

[YNOTAZ]

Now that you have it, F Y I. My AR-V doesn't run well with Magpul mags. It does with CZ and PSA mags. If you invest in Magpul don't buy a bunch until you see if they work. I have a CA, AR-v and AK-V and Magpul mags are the only mags that had failures.

 

[campinginaz]

Bought a PSA AR-V 8" 9mm this weekend after looking through this thread

Nice!

 

[campinginaz]

Bought a PSA AR-V 8" 9mm this weekend after looking through this thread

Nice!