Can I use an A3 upper with a 9mm blowback?

AR/M4 AR Pistols & Pistol Caliber ARs
1

I’m asking because I recently purchased a forward assist gas vent but decided against using it on a 5.56 upper. It would be a nice, relatively cheap alternative to getting a PRI charging handle and be more effective.

Also, since the F/A can’t be used on most (all?) 9mm bolt carriers and the F/A gas vent removes forward assist functionality, I wouldn’t be losing anything either.

My main questions are:

  1. What to do with the gas tube hole in the receiver? Fill it? Leave it?

  2. Since the shell deflector is smaller, how would that affect operation?

Thanks!

2

to fill or not to fill well that would be your choice but I would maybe put a plug in just to keep dirt and junk out I wouldn’t pay to have it welded .

The only time i shot a 9MM AR the shell defector really didn’t do anything the Colt defector snapped on and off and if I remember(sorry been a few years back )the rounds landed about the 2 to 3:00 o’clock position.

I don’t think you would have a issue ,But I am sure someone that owns one would be more help just thought I would tell you what I thought:D

3

I have a 9mm built with an A3 5.56 upper, it has the gashole drilled and causes no issues at all so I would leave it.

As for the shell deflector, I have the one installed for 9mm and I think if your not a lefty then it also is not neccessary.

Here’s a pic of my 9mm.