SINCE I CAN'T POST PIC HERE  SEE LINK https://forums.brianenos.com/topic/268449-cmmg-guard-tuning-kit/

CMMG has replaced some bolt and carriers for failure to eject and bolt over base jams. My new bolt exhibit excessive recoil impulse when compared to the original bolt, similar to a regular blowback.  See pics. I believe they changed the bolt locking lug angle and possible the cam slot in the carrier.  Even with a 308 flat wire recoil spring and HYD buffer bolt speeds were too high. All development using federal 9mm 115gr Alum rounds. So I ordered the tuning kit.  I installed the 2.0 oz carrier weight and now things are back to normal. The increased carrier weight slows down the unlocking because of increased inertia, no amount of recoil spring weight changed the carrier velocity.  Read the instructions sheets for more details of tuning. Happy again and with a very soft shooting

I've completed my full auto Guard tuning and posted my results here: https://www.ar15.com/forums/Armory/Full-Auto-CMMG-Guard-Tuning/23-494385/
In my testing, I've found the static weights to be too bouncy for my tastes and resorted to my own tungsten spring loaded weight in the carrier as mentioned in my link above.

Right click image

Copy image address

click image icon on ar15 posting window.

Paste the image link in the pop-up window

I Enjoy reading your post, what struck me the resemblance to was Sullivan/Surefire advanced bolt carrier solution. Too bad high speed cameras are so expensive. I wonder does the Guard suffer from bolt bounce. Your experience points to it. Things like flat wire, hyd buffer, and carrier weight all tame bounce. Also look at Taccom spring loaded buffer.  Too bad magazine like precision shooting don't exist any more I really enjoyed that mag. Adding the 2oz weight has made me happy again with  my guard.

Thanks for info

I don't know if you've looked at my site here: http://c3junkie.com/?page_id=538
I go over more details and discuss the Sullivan/Surefire as well as the Master of Arms carrier that has a captive weight that is spring loaded on both sides.  I have played with captive non-spring loaded carrier weights and since they are captive, they are able to force energy into your shoulder...they do run slower but I believe not as as smooth.  I believe that by not having the weight captive, the weight isn't able to 'pull' the weight back since it is free to move on its own.
I only want the weight to affect the initial recoil impulse and to aid in getting the bolt into battery.  
Of course, the weight doesn't just disappear on the rearward stroke but I think not being captive helps in in smoothness.

I would like to test with a non-captive setup with springs on both sides of the weight but just have so little room to work with on the Guard carrier unless another hole is drilled and move the pin forward.
I have a cheap Casio Exilim camera that can do 240, 480 and 1000 FPS.  480 is good enough to see bolt bounce.  I haven't used it on the Guard but do know that it suffers from bolt bounce.  Using the standard JPSCS results in bolt bounce with the Guard as well as high cyclic rate.