I did...look at the previous page of this thread: https://www.ar15.com/forums/industry/Bearing-Delay-Upper-Receiver-Assembly-updates-information-and-resources/817-303326/&page=4
You would have to ask MEAN if they will sell you a spare barrel or extension but doubt it.  Your end goal is do an SD build but they are already working with I think https://hitecarms.com  on a SD setup.  So they may want to do their own internal testing first.

Not fair to say that.  I'm on my 3rd ejector spring on my MEAN in less than 2000 rounds.  Nothing is perfect.  
I have stated many times that I was never impressed with the out of the box recoil impulse of the CMMG Banshee or Dissent.  Better than straight blowback but like 60% there compared to straight blowback but a tuned CMMG RDB can match the MP5 with a 'better' cyclic rate than the MP5.  Most people running CMMG's Banshee's don't care about tuning until they start to fail and most don't know what smooth is as they haven't shot anything better side by side.

The CMMG Dissent fixes the failing ejector spring problems since they finally went with a fixed ejector eliminating that from the maintenance schedule and point of failure.  I would be ecstatic if MEAN did the same.

Read the MEAN manual which clearly calls out wear item parts, like the ejector spring, ejector retention pin, extractor spring as well as the ball bearings.  
Nothing lasts for ever and it is to be expected for any delayed system where parts are impinging on each other.
My tuned hybrid Dissent has not missed a beat since I built it which uses a fixed ejector.  I run this full auto and suppressed with a tuneable full auto cyclic rate.
The CMMG delay comes from the angled lugs on the bolt and the lugs in the barrel extension which are standard.  Several people have made their own CMMG compatible barrels including myself.  
I have a custom stainless CMMG RDB barrel with over 50K rounds on it and there is no detectable wear on the extension and if there was some, I could swap it.  You can buy spare bolts and BCG's from CMMG.  Can't say the same for MEAN yet but yes, you can buy the lifters.  
Extra barrels are not yet available for the MEAN and now look at all the proprietary parts in the BCG for the MEAN.  
I would say my MEAN with the K lifter is slightly softer than my tuned hybrid CMMG Dissent but the ejector I have in there is fixed and will never fail and doesn't have a maintenance schedule that is clearly an advantage over the MEAN.

For me my order of preference 'today' is:
1.  My tuned hybrid CMMG Dissent with the fixed ejector and custom made carrier extension for tuning w/ buffers and springs as well as to trip the auto sear documented here: https://c3junkie.com/?page_id=1733
2.  MEAN Arms is only second since it still uses an ejector spring that is inline with the recoil impulse and I'm already on my 3rd one in under 2000 rounds.
3.  CMMG Banshee and deal with the ejector spring failures as well.

Now if we are talking semi auto only and not full auto like I want my preference would probably be for someone that didn't want to go with any custom parts
1.  JP-5
2.  CMMG Dissent  - I would move that to #1 if you are OK with custom parts or if you have a SBR lower since the JP-5 is using a proprietary upper/lower receiver length.


ETA...At last month's SMG match, I ran my hybrid CMMG Dissent which ran 100%.  2 guys brought their MEAN uppers.  Both had around 300 rounds on them before the match.  1 guy ran his for only 1 stage with no issues.  The other guy ran all 4 stages with his MEAN and it was a disaster.  I was the RO for him and saw several times where he had a live round facing back at him which was really weird as well as some FTE's.  

Well hell amphibian!!! Thanks, I had no idea there was an integral coming out. Looks like all I need is some patience and to shoot the CMMG until the extractor fails and then buy another mean arms uppers.

that plan works for me, time to sell off all the other crap I've accumulated for these builds.

CMMG's typically don't have EXTRACTOR failures...it is the EJECTOR SPRING that fails....
and again, the MEAN isn't immune either.  I'm on my 3rd EJECTOR SPRING on my MEAN in less than 2000 rounds of full auto / suppressed.

My hybrid Dissent build utilizes a fixed ejector which removes that point of failure.
I believe you are running full auto suppressed with a RLL?  I would wait till you have several thousand rounds through your MEAN before buying more...although, I'd be happy to sell you my MEAN upper if you want.

This past weekend Zack Smith won the PCC division at the Rio Salado 33rd Annual Spring Steel using the Bearing Delay system!

I appreciate your dedication Amphibian. You saved me a lot of headache and heartache, by explaining the short falls of both the Mean and CMMG RDB systems. I'm looking forward to your completed write up on your custom Dissent and will probably go that direction if it is possible for me. Right now I'm really liking my 90% set up with the 9mm RDB bolt and barrel, Tubbs 300blk flat wire spring, and 5007 Hydraulic buffer. I allowed my wife to shoot it so she could compare it to her blowback AR-V and she didn't want to give me my weapon back. It was really a night and day difference.