I'm thinking of building an AR9 with a tucked suppressor.  I have a 9.3" aero enhanced handguard.  The relatively wide one, the internal dimensions on are 1.7" IIRC.  I also have the aero enhanced assembled slick slide upper to go with it.  The barrel will be a CMMG 5" with bolt.  I have a few stripped lowers laying around so one of those will do fine.  As far as the buffer and spring to be used with an RDB kit, what are the recommendations?  standard buffer and spring.  Or do I want a Tubbs flat spring and some other buffer weight?  I know on the CMMG bolts you can tune them by adding weights so I wasn't sure if the buffer and spring needed to be as thought out as a regulars AR
would be.
The cans that I would use would either be a Ghost or a Wolfman.    Any thought or recommendations would be welcomed.  The lower could be either dedicate to this upper or if possible be able to be ble to run on a AR-15 upper as well.     Sorry kinda rambling, these are a little out of my comfort zone as far as building.  I've built plenty of regular ARs through the years though.

teach me like I'm 5. so to speek.

Standard carbine buffer and spring should work fine.

cool

Buy A Foxtrot Mike 9mm Native Upper and Lower and be done with it.

I bought a Scorpion (meh) then I built and AR9.   I love the AR9 so much more...  Especially suppressed.  Shooting steel is a hoot.

Looks like you're going with CMMG RDB, may I suggest getting their conversion magazines also - https://cmmg.com/magazine-9-ar-conversion-30rd

I am running the original version (Endomag) magazine set up with my 9mm upper in a standard lower (binary-trigger equipped ) and it is working good, allowing me to use the same 223 mag pouch.

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Research proved that I need to learn more about AR9 before commenting about them.

I just confirmed today that CMMG has discontinued all of their straight blowback 9mm products just an FYI.

It sucks as their bolts were awesome.

I just picked up an 8" barrel and RDB bolt as a backup for the banshee that I have.  Still waiting on the 5" to come on stock.  I have about 10 in stock alerts set.

I had a 9mm 16” RDB stitched together by my gunsmith. CMMG recommends a standard carbine buffer & spring, unsuppressed. Their conversion kit for blowback-to-RDB (that I used) had that exact setup in it.

I used a JP captured setup, and optimized for functionality with standard pressure 124 grain from the smith, the three weights are all just steel, with the standard weight spring.

Once my Omega 45k comes in, I’ll have it back off again for suppresses tuning, and we will see about the difference between the “bolt tuning” weights, the JP weights, and the suppressor.

Save yourself a crapload of time, money, and aggravation and just buy it.

This!
and add a magpul pcc 50rd drum.  

Honestly, the RDB is a much better system.  That and those Glock mags lowers look like shit.

Yes, the CMMG recommendation is a standard spring and buffer.  However, I think that is to maximize it's operating window as they don't know what kind of ammo or out of spec parts someone may use like maybe a tight upper or rough buffer tube.
IMHO, when I first tested the CMMG RDB with a standard spring and buffer I wasn't that impressed.

I have a ton of info on the CMMG RDB on my site here: https://c3junkie.com/?page_id=164

Here is a high speed video I did of what the recoil impulse looks like with the standard buffer and spring recommended by CMMG:



Now, here is what it looks like after using my recommended buffer, spring and tube:
I know in that video I'm using a modified 5.45 bolt as well.  Even using the standard CMMG bolt, the impulse will be much improved.



In summary, I would recommend to initially use their recommendation of a standard buffer and spring as your baseline.  If it doesn't work, you can always go back to them for assistance. If you are happy with it then then you are done.   If you want it tuned more, you sure can which is the beauty of the AR platform.

This is what I have put together so far. The bolt and barrel should be here tomorrow, 5" cmmg RDB. A mock with a ghost is in the pics below.  I have a Wolfman in jail that would be in there as long as it's not too wide.
Also my first time attempting cerakoting myself, the color is charcoal green.
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That looks a lot better than my first cerakote attempt.  So far, so good.

RDB bolt and 5" barrel came in today.  AR9/SD without the barrel porting.
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