So, I am jumping into the PCP AR world by building my first 9mm AR. I want the pistol primarily for indoor range practice, so common controls are important to me. I intend to use a standard forged AR lower with the MEAN Endomag. I have read numerous posts and build specs, but look to this group for some explanation and guidance.

Do I need to use a special upper receiver for a 9 mm AR?

What is the advantage of using either a .458 SOCOM upper receiver or a billet 9mm receiver?

You don't have to use a special receiver for the 9mm. You definitely don't need a .458 upper. A standard 5.56 receiver will kick out 9mm casings just fine.

I wanted a more traditional look for my CMMG, so I found a slick side that takes a dust cover, and added a gas deflector and the short door. A case deflector and forward assist is a waste for a 9mm.

Billet vs. forged? Cant really speak intelligently on this other than billet uppers that I looked at were fancier, had side-charging, or fancy milling. Forged is going to be a regular AR upper.

My 6.8 SPC pistol has the Pantheon Arms Prometheus MC system on it. I think I could simply buy a second Prometheus, a barrel, BCG, buffer, and spring to get started. Reuse the complete lower, upper receiver, and optic.

quote:

MEAN Endomag

I don't know anything of these personally. Are they even shipping? Sounds good but not sure if they actually work. I use a mag insert.
In terms of an AR 9mm upper almost anything can be made to work. But there is no point in using one with a forward assist. And I prefer the actual 9mm ones with the correct dust cover and short door. After that mostly you need to respect lower issues on the hammer and bolt compatibility.

The Endomag has not started shipping, yet.

A billet 9mm upper will be setup for the shorter cartridge and have a smaller ejection port. Forged uppers will be standard AR geometry.

Mine is a forged slickside, no dust cover, shell deflector, or forward assist. The lower is a standard config with a Colt style mag block held in by the bolt catch. It's a full Palmetto kit with a 16" barrel. Tons of fun on close range steel, point-and-click using a red dot.

I've seen a mag block that feeds from the bottom and uses a screw to tension itself. It's for Glock mags. Might make for an easy swap on the lower, and if you already have Glock mags and don't want a dedicated lower might be another good option instead of converting standard AR mags.

I believe you can use a Vltor A5 buffer in a standard tube on a 9mm setup to shorten the stroke of the action, also would be a good way to identify your 9mm buffer setup if you don't use A5 in other guns.

You can get a 9mm bolt with forward assist serrations.
I'm not saying it is necessary, just that it is available.

Spinta Precision 9mm angle cut BCG.


A far as the MEAN endo mags; by the time you buy the kit and add it to a PMag, you have a final cost that is more that a dedicated 9mm mag. While they tout being able to switch back and forth between 5.56 and 9mm, I doubt most people are going to be switching the guts out of the mag every time they want to shoot.
Personally, I prefer having a dedicated 9mm lower and dedicated 9mm mags. Colt style mags already have a last shot bolt hold open.

I use the Rainier upper with no Forward Assist for my PCC.

https://www.rainierarms.com/ra...pper-minus-fa-22-lr/

I bought a few blems a few years back for $50 a pop. Can’t find the blend and are a fantastic part.

Though at the time they did not have the 9mm/.22Lr designation in the title. So not sure if there is a difference between what I bought and the link.
They look the same.

Anyone have a link to the Endomag?
I am only finding Endomag Medical Devices.

Thank you for the information.

Link to Endomag:
https://www.meanarms.com/produ...endomag-9mm-preorder

I’ve built a couple off regular Aero uppers. I don’t care for the look of uppers without forward assist. No issues.

I’ve preordered the Endomag setup. The benefit for me is the use of one of my SBR lowers with a legit stock. No reason to Sbr a dedicated Colt pattern or Glock pattern lower, no mag well adapters. Same size mags as the rest of my AR pattern rifles.

I do hope they work as advertised!

I bought a Colt 9mm SMG demilled kit, came with everything, including the 3-round burst FCG which fit my M16 receiver nicely. All Colt parts that came from the same gun so there was no trial and error. The receiver block was originally pined in place but I wasn't going to do that to my receiver, but the block also has 2 little tension pins that tighten with an alan wrench so the mag block doesn't fall out when you drop the mag, and it had the correct spring & buffer ... Every thing except the receiver.
I can also put it in any of my other semi-auto SBR'd lowers and it runs perfectly in them too as long as I use the correct buffer and spring.

quote:

Originally posted by burnetma:
Thank you for the information.

Link to Endomag:
https://www.meanarms.com/produ...endomag-9mm-preorder

Pretty slick, if it works, and is not vaporware.

Guess, I’ll preorder one.
Says late summer. Wonder when or if we’ll actually see them.

This message has been edited. Last edited by: Black92LX,

My 9mm AR uppers use standard receivers. I use a CMMG 9mm lower and a standard lower with Hahn mag block.

That Endomag looks pretty interesting.

quote:

Originally posted by Black92LX:

quote:

Originally posted by burnetma:
Thank you for the information.

Link to Endomag:
https://www.meanarms.com/produ...endomag-9mm-preorder

Pretty slick, if it works, and is not vaporware.

Guess, I’ll preorder one.
Says late summer. Wonder when or if we’ll actually see them.

I figured I had little to lose. If it works, great. If not, I am out $30.

I read on another site that MEAN is targeting shipping the first units the end of September.

quote:

Originally posted by burnetma:

quote:

Originally posted by Black92LX:

quote:

Originally posted by burnetma:
Thank you for the information.

Link to Endomag:
https://www.meanarms.com/produ...endomag-9mm-preorder

Pretty slick, if it works, and is not vaporware.

Guess, I’ll preorder one.
Says late summer. Wonder when or if we’ll actually see them.

I figured I had little to lose. If it works, great. If not, I am out $30.

I read on another site that MEAN is targeting shipping the first units the end of September.

Same here since I pulled the trigger on a preorder.
$30 no big deal. Would be more disappointed it never made it to market gs the loss of money. Looks like a sweet idea.