Anyone here have a semi SBR uzi. I built one and want to put my octane 45 on it. Just curious how it compares to a suppressed handgun in sound.    
      I load 125 grain rn with 3.6 gn red dot. Most of them functioned, I shot zome 115 tula and no malfunctions.
     I think I saw a thread in which someone posted the quietest PCC was mp5 followed by uzi or mpx and then maybe ar15.
   If any of you have one or shot one give me your opinion please.  I have looked at YT videos but you nevrr get a feel for the actual report from them.
  It was built as a pistol but all shooting has been with the 16 barrel and bolt from my model A.
 I'm thinking of getting a 45 kit for it.

Try 147gr - very quiet.

The quietest PCC is a DeLisle. But that's a bolt-action, integrally suppressed 45 ACP rifle built on an SMLE.

Mp5 is quieter, but the UZI is still quite. You mainly hear more action noise on the UZI with the big heavy bolt slamming back and forth. 

I have an Uzi, and an MP5, suppressors for both, and reload my own ammo.... but there is no way to answer your question because there are too many variables.

I have a giant Uzi suppressor by Coastal, an MP5SD with a TSD can, and a standard MP5 I can put a number of muzzle cans.  With my 147 grain reloads, they're all really really quiet.  They are all significantly quieter than any of my suppressors on a pistol.  An Uzi barrel is two or three times longer than a pistol barrel.

Thanks everyone for the replies, I ordered a 10.5 threaded barrel. After shooting I will post back with my opinion of it's sound level.

Try 3.6 gr of VV N320 behind a 147 gr FMJ...

For whatever reason, the Uzi suppresses very well.  I've run 4 or 5 different cans on mine, from full-sized dedicated SMG cans to the "do-all" pistol cans with a solid mount.  

Most of my experience has been with the open bolt setup, but I've run them closed-bolt as well, and they also seem to do very well.

I finally got out and shot the silenced Uzi with the 10.5 barrel. This has quite a bit  less report than the glock 19 with the same 125 grain load from my initial post.  I am very pleased with the Uzi suppressed, I'm going to get some 147's or maybe get a Lee swaging die and swage down some 158 38SPL TO .356 and try those.

You might try slugging your barrel first. You may find you don't have to size them down at all. I find many of my 9mm barrels are .3570" or .3575", including most of my Uzi barrels.

Also, see my comments Here.

Thanks for the input everyone  it's appreciated.

As mentioned, the mp5 is quieter but my mini uzi with 3 lug is so quiet and no gas at all in my face. It is a great host!