Does your rifle/pistol have an adjustable gas block if not you might want to get one, and if it does have one are you familiar with how to tune your adjustable gas blocks?

 

The gas block only has 2 settings.

Im going to try a different suppressor and if that doesn’t work I’ll have to look into adjusting the gas block.

thanks for the info and video.

 

Here’s a video on it, but there are many on the internet.

 

Not speaking from first hand experience with this setup but I've got several flow through cans and multiple MCX uppers. I've had issues with cycling subs with flow through cans in mcx and AR uppers. I'd have to double check, but sig was supplying some uppers with an extra gas plug for usw with their flow through cans. No idea how big the port has to be to get subs to cycle.

 

That’s one of the problems with proprietary hardware, I have an Sig MPX K and I knew it only has two settings on or off so I went with Sig MODX9. When you have built your own AR’s it pays to go with adjustable gas block then you can use whatever suppressor you want.

 

Here’s a thread on it as well.

https://www.sigtalk.com/threads/mcx-5-56x45mm-carbine-gas-settings.68866/

 

I just bought a CAT ODB for my MCX. Haven’t picked it up yet. I’ll let you know how it does on there since I have a complete MCX. That shouldn’t make a difference tho. How quiet was the can?

Wait so you a running a 223 bullet through a suppressor that has a 354 hole? I’m not an expert by no means but couldn’t that be too large a hole to keep enough gasses in to cycle the bolt etc…

 

Shoot a few boxes of supers, then come back to the subs.

 

TLDR: My recommendation I've spent the better part of a year working out this problem and documenting it. I've got a newborn so I won't be able to answer a ton of questions. I'm running a CAT MOB or a CAT Dirty Dave out of my 5.5 Rattler. I couldn't get my Hyperion to run well until sig opened up the gas port which I do not recommend as now my gun is overpassed even with these high flow rate suppressors on there.

DO:

• Rinse your suppressor in the faucet for 3-5 minutes incase there's left over TI dust in the suppressor from the additive manufacturing process . Which send talcum powder like substance back into your system which can and will cause the MCX to fail to cycle. This a known thing with the PTR and CGS Hyperion CGS does manufacture CAT suppressors but I've rinsed all my 3d printed cans since I've had this exact issue
• Then field strip and clean your gun
• Run about 500 supers and clean again
• Try to run subs on the + setting, if it continue to be an issue you're going to need to make a choice
• I recommend cutting a ring or two on each side of the springs this will allow the weapon to cycle with subsonic pressures. New springs are $100
• Try a Fo3 Gas valve ($150+)
• use a high back pressure suppressor if you have one (surefire socom 300 sps)

DO NOT:

• Do not send this back to sig or send it to a gun smith. They will simply drill a bigger hole in your barrel's gas port. You don't want this because it's going to make an already gassy host. INSANELY gassy as can be seen here
  Replacing a barrel after they make this fix is ($900) Although this is a 5.5 barrel your 9 inch barrel should be less gassy as the propellant is getting burned up while traveling through the 9 inch barrel.

Alright so I was having the same issue

out of my 5.5 rattler with the f02 gas plug. I used a CGS Hyperion, CAT MOB, CAT Dirty Dave on my rattler. At first none of them would cycle.

Essentially the MCX platform with 300 blackout subs required backpressure. I've seen some folks have no issues with the CAT ODB, I've seen CAT recommend the JL because the MCX requires back pressure for subs. Although I've seen successes and failures with the ODB.

My friend told me to clip the springs to "soften" it up which will allow the bolt to travel cycle with subs. I thought it was ridiculous and had to be something wrong with the gun. But with most platforms you want to tackle everything you can before you start messing with the gas.

Also once you get it running with the CAT MOB or a high flow rate suppressor it will run well, just remember this isn't the best suppressor host IMO.


Attached another fun fact: Did you know this GAP in the MCX platform (including newer LTs) is within spec according to sig? The other photo is the unburned particulates being shot up into my nose and eyes when using the CGS Hyperion after sig did their "fix" Ala open up the gas port at the barrel.