u/Jim_Jabroni

I decided to just make a new thread about the barrel nut setup for my AR9 integral suppressor build.

The barrel nut and tubing sections were made by my machinist buddy. The sections were originally made to be a modular extension for 1.75” tubes.

Original thread:

Barrel nut:
- Exterior threaded for presma handguard
- Interior threaded for standard AR receiver
- Distal end threaded for 1.75” tube

Tube sections:
- 1.75” OD, 1.639 ID
- 2.5” total length, 2” when screwed in
- roughly 1.5” of useable space in each section

Ideally, I would use a long 1.75” tube so I could take advantage of spacing things exactly how I want, with no lips inside the tubing. Not optimal for spacing but it should work well, especially being 1.75”.

Now, he’s designing a new barrel nut setup for my FM9 that will hopefully be done this weekend. It will be the same as this one except with male threads on the distal end to accept a SDTA 1.5” tube. He is also going to machine an adapter that will thread onto the barrel and has a built in 1.355” diffuser wall. I’ll have more info on this hopefully by early next week or sooner.

I’ll post pics as soon as I have them. If there is enough interest, he’s willing to make more.

Pic of full setup: https://imgur.com/a/tHNHxE5

I should also add that my goal was to slow down 115s and 124s, hopefully to subsonic. I use syntech 150s in my suppressed FM9 but they are more expensive and I’m cheap 😂

Host: AR9 w/ 1.75” OD integral suppressor tube in 5 sections

I took a D cell FTN5 max turbulence 9mm baffle and adjusted it to fit into the 1.75” tube. Only the last 3 sections will have baffles due to the barrel. The first of these 3 sections will have an inconel diffuser wall before the first baffle.

Option 1: diffuser wall + 3 long baffles (each ~1.5” long )

Option 2: diffuser wall + 6 short baffles (each ~.75” long)

I have a ton of unused stamps so I could just print whatever and try it both ways but I’d like to nail it the first time.

Pix 2&3 are of a long baffle filling a section for visual reference .

** I have a FM9 running like a top with a super safety along with several other 556 and 7.62x39 ARs. I also researched this issue and the fixes aren’t working.**

Just got this Aero EPC9 lower and went to install a super safety but it is binding on the trigger. Trigger will not move at all in safe. I ground a dimple into the trigger but it is still binding 100%. I don’t want to get any closer to the rounded corner so I’m not sure what else to do. Don’t want to ruin the trigger.

What about grinding a divot in the floor of the pocket to allow more space for the trigger to move? I already opened up the edges of the pocket (as you can see in pic) bc it was tight.

Using a MuffinTop Tactical SS, same as my others that work perfectly.

u/blowback9 or any others have any ideas on this?

Trigger not moving in safe: https://imgur.com/a/3D8dWLs

I ran a drill bit (by hand) to lightly open the hole in the charging rod for the Allen wrench but it split when I went to put the wrench in.

I tried a 5/32” and 4mm but both seem too big for the rod.

Is it a print issue that the hole is too low (pic 2)?