Is it strictly necessary to use a dedicated PCC stripped upper, or can an ordinary AR upper work? Dedicated stripped uppers seem pretty costly, but maybe the ejection port size keeps brass cleanly ejected? Thanks in advance.

A normal upper will work. CMMG actually recommended an oversized ejection port for their 9mm system, so I went with an Aero XL upper...I've had zero problems with it.

Thank you; that will make it a lot less costly.

I do not understand. You need a barrel, bcg and other items. How much are you saving?

quote:

Originally posted by old rugged cross:
I do not understand. You need a barrel, bcg and other items. How much are you saving?

This isn't about an overall build price point, but a single component cost. This has nothing to do with pinching pennies. It's a matter of do I need to spend more for no reason; $35 regular or $70 PCC is roughly the current spread on commodity-grade stripped uppers. Now, if I had been advised that Yes, a smaller or more precisely-placed ejection port is necessary for clean ejection, the price would've been worth the premium.

From what I've seen, once you got to boutique milled stuff or big name brands, the price is pretty much a wash.

I have no idea from personal experience. I'm sure there is enough web info to get some advise. But I started my 9mm carbine 'adventure' many many years ago with a colt. And colt changed the ejection port. Now if it didn't matter then why would they. Maybe it only matters in a subgun. I have no idea. But I have duplicated the colt 9mm upper in every gun I have built.
But in this case you are risking almost nothing to try a std. upper. Worse case you have an extra upper...

quote:

Originally posted by hrcjon:
I have no idea from personal experience. I'm sure there is enough web info to get some advise. But I started my 9mm carbine 'adventure' many many years ago with a colt. And colt changed the ejection port. Now if it didn't matter then why would they. Maybe it only matters in a subgun. I have no idea. But I have duplicated the colt 9mm upper in every gun I have built.
But in this case you are risking almost nothing to try a std. upper. Worse case you have an extra upper...

Fair take, and Thanks. I haven't bought one, yet. Stern bolt and Matador magwell are here, and barrel is incoming.

Colt's 9mm conversion adds a 9mm shell deflector which shortens the ejection port opening, using a standard port cover that's cut down to accommodate. The 9mm bolt doesn't need to travel as far rearward as it extracts in a shorter distance.

With a standard M4 upper the shell deflector is useless, the ejection port is longer than necessary, the gas tube hole is not needed, the feedramps are not used, and the forward assist probably won't work as 9mm bolts aren't normally cut with the forward assist notches. Most 9mm uppers omit or change these aspects as part of their design.

You can use most any "standard" AR upper to build a 9mm.

Thanks hrc and rust, pretty much confirms my thinking. I see no benefit and several potential issues that may or may not arise. I just do not see the value in it.

quote:

Originally posted by old rugged cross:
Thanks hrc and rust, pretty much confirms my thinking. I see no benefit and several potential issues that may or may not arise. I just do not see the value in it.

Alright, what several potential problems are your perceiving that "may or may not" manifest? I already addressed ejection concerns in the opening post. I asked for advice if it'd work, so if you have practical experience, I'm all ears.

Not really, just as I said. Seems like a solution in search of a problem.

Curious how expensive a dedicated upper is in comparison?

quote:

Originally posted by old rugged cross:
Not really, just as I said. Seems like a solution in search of a problem.

Curious how expensive a dedicated upper is in comparison?

No, you said several potential problems you could see. You get confirmation bias from a couple of posts and ignore one that says a regular receiver is fine. All I wanted to know was if there would be ejection issues.

The internet is full of pre-built uppers for you to price. But I'm wanting to build one, and there's things about it that dictate some specific components and some (like receiver type) that may not matter.

So doing some surfing as 92 say's and many other sources say, yes. Use all you want. Not seeing a lot of ejection issues. A few.
Doing it that way would not be my choice. Ymmv

Maybe ask the manufacturer of the upper you plan to use.

A normal upper will be fine.

The doodle on the side of the Colt is for gas blowback, not a shell deflector. It's designed as a submachinegun. (semiauto) 9mm uppers without it don't suffer issues. You adjust ejection with spring and buffer weight.

There are common issues people suffer with 9mm guns, but many boil down to the ammo. It can't be weak. If all you shoot is WWB, then you're going to have problems with a spring and buffer meant for defensive ammo, and vice-versa. One won't cycle, the other will beat the hell out of the gun.

Make sure you ramp the carrier, so you can use any trigger group. Without the ramp, rearward velocity will punish the trigger group and if you really pay no attention, elongate the holes in the lower (the differences in "stock" colt 9mms are all about the beating full auto dishes out. Without the ramped carrier, you need to pay attention to the design of the hammer itself.

quote:

Originally posted by arcwelder:
A normal upper will be fine.

The doodle on the side of the Colt is for gas blowback, not a shell deflector. It's designed as a submachinegun. (semiauto) 9mm uppers without it don't suffer issues. You adjust ejection with spring and buffer weight.

There are common issues people suffer with 9mm guns, but many boil down to the ammo. It can't be weak. If all you shoot is WWB, then you're going to have problems with a spring and buffer meant for defensive ammo, and vice-versa. One won't cycle, the other will beat the hell out of the gun.

Make sure you ramp the carrier, so you can use any trigger group. Without the ramp, rearward velocity will punish the trigger group and if you really pay no attention, elongate the holes in the lower (the differences in "stock" colt 9mms are all about the beating full auto dishes out. Without the ramped carrier, you need to pay attention to the design of the hammer itself.

Thank you for the advice. I've got a lot to sort one everything's here, it seems. I've also been watching Blowback 9's YT channel for tips. I did find a 9 upper for a reasonable price, so it's on the way.

Thanks again, all. And ORC, thank you. You kinda missed my intent, but I know you had your head in the right place of optimization concerns.

If I recall correctly, the main issue with ejection ports is using it for 40 or 45 acp. Ypu can modify a regular upper yourself by dremeling the port a bit, leaving some at the ends for the cover to stop against. Otherwise the pcc uppers usually are slick slides without a gas tube port, but using a 5.56 one doesn't usually cause problems, it just if you want a "proper" upper.

I would suggest trying it and if there is a prob, modify or get a pcc upper.

In the old days there was small dimensional issues with different brands, mostly that some systems needed the mag to be held at exactly the right height, which you could do with the mag inserts. These days it seems like everyone is playing to the same spec and most people's stuff play ok together (kinda like f height front sights used to be a big deal but not so much anymore or most bolts are now ramped and cut to work with bolt colt and glock mags).

The only thing I reatruck. These days is either use a 9mm long buffer or the quarter trick.

I cheated and bought BCA's Complete M4 9mm Upper. The upper is a standard AR upper with Forward Assist, only thing different has 9mm BCG with Glock cut face.

Got it all together a couple of weeks ago. Commodity-grade Anchor Harvey PCC upper forging with Matador magwell adapter. The barrel is Kaw Valley, and it runs perfectly, fun, and relatively inexpensive to shoot as well as build. It's been so satisfying that I paid for a stamp and one-shot trust for a suppressor last weekend.

Thank you all again.

Congrats Opus.

Skng that sounds like a good choice too.

Hey ORC Your post actually made me do a little more digging and I found that upper at Gorilla Machining.