9mm Uppers

[blksno]

Is there anything mechanically different about a pistol caliber (9mm) AR upper receiver or more specifically, will the rifle still function properly if it was built on a standard upper, rather than one designed for 9mm operation?

The only thing that looks different, are the ones that have no forward assist, no standard shell deflector and a modified shell deflector/ejection port door.

In using a regular .223/556 ejection port, will the brass simply eject more toward the rear, or will it cause malfunctions?

 

[707electrician]

Re: 9mm Uppers

I believe a standard upper will work fine, you just need the 9mm bolt carrier and hammer

 

[Krazny13]

Re: 9mm Uppers

Don't need the 9mm hammer if you use a ramped bolt OR neuter an M16 hammer by removing the sear hook.

Normal upper would work, but you'll have more gas blow by due to the method of operation. The FA, deflector, and normal sized port/port cover aren't used because they are not needed for 9mm.

 

[dogman]

Re: 9mm Uppers

You'll need a mag adapter as well.

 

[blksno]

Re: 9mm Uppers

Thanks guys.

I've got the fire control group covered, I've got the BCG covered and I've got the lower covered too. It was just that upper that had me mind boggled.

Looks like "Operation: BLIZZARD" is a GO

 

[jink122]

Re: 9mm Uppers

I was wondering why some bolts needed ramping. Thanks.

 

[mavrick10_2000]

Re: 9mm Uppers

Any upper will work.

However if you shoot suppressed the deflector is actually pretty decent at directing gasses away from your eye. It's more of a gas director than a brass deflector in 9mm.

Like the other posters stated no FA needed, it's another gas leak and will piss you off shooting suppressed when you get some extra gas in the face.