My understanding is that the 9mm uppers are blowback design.

So how exactly does that work?  Does it fire from a closed bolt?

I would guess that the bolt does not rotate, so does it have a carrier?

Is the operation of the lower similar to when the DI upper is used?

Does the buffer cycle the bolt?  

Thanks

I'm just curious, i've never seen a 9mm upper in person, i've been sitting here for an hour trying to imagine how it works.

The quick answer:

it is blowback, it fires on a closed bolt, the bolt has more mass than a standard bcg as does the buffer. Everything else is the same as any other AR except maybe the hammer and it requires a mag block insert unless you have a dedicated 9mm lower.

Even though it is not...think of the bolt as one solid machined piece. Not a separate bolt and carrier.Kinda like a semi-auto 22lr

If you have access to the internet, you could have probably spent 5-10 minutes on google and the other 50+ minutes doing something else...

LOL some times you can be a funny peckerhead
Thats ok though as I was gona give him the link to google and be a bigger peckerhead.
lotsa pictures and how over here

well, arfcom has an army of bona-fide AR15 experts.  that is very unusual in the gun world.

maybe you don't realize, but the typical "gun fact" is just basically some random crap that people just repeat over and over again.

like for example, if you tried to figure out what the best suppressor for the money is, you might google for months before you actually found an opinion based on testing, data and logic.

so by asking this question here, I'm tapping into a source of information that's from people who are dead serious about actually buying and using the product

By the way, during WWII, the japs could fire our ammo in their guns, but we couldn't use their ammo.  Pass it along.