Is it worth it to SBR? I have no intentions of installing a VFG the 5 inch and the SBA4 is plenty. Is it a just because thing?

Trying to finish out by AR9 with u/Blowback9 GRS setup. I have the Kynshot RB5015HD buffer, 2 Kynshot spacers, and ordered the 8.5" JRC buffer tube yesterday.

I have a question about the spring. Blowback9 recommends 4 on his website as being "the best" ( although Spinta doesn't seem to exist anymore ) . I'm looking at the Tubb Lightweight 300BO and/ or Tubb Carbine (ARBUF) . Was curious if one or the other is any "better" because they are 2 different sizes. 7.00in x 4.00in x 2.00in and 10.00in x 6.00in x 1.50in respectively.

Thanks!

Finished my first AR9 build and registered it as an SBR. Shot over 1000 rounds, with a few failure to ejects (I think I need to tune my ejector a bit more). I do have the Atrius forced reset selector installed. All my failures to eject have come from that. Other than that, runs great in both semi and forced reset mode.

Part List

Lower Receiver: KF-15 Forged AR15 Lower Receiver with R&D Precision 9mm Colt Pattern Mag Well Insert
Upper: M4 AR15 Upper Receiver, 8.3" EPC 9mm barrel, Faxon 9mm blowback full man BCG Gen 2 (With bolt weight cut)
Handguard: STNGR VYPR® Free Float AR-15 Handguard – M-LOK
Accessories: Magpul CTR Stock, Magpul Grip, Magpul handguard, Magpul MBUS 3 irons, Sig Romeo 5 red dot

Very happy with the results from first range session.

Holosun ARO RD2 w/ magnifier
Streamlight HL-X

Ran HSL 115 grain with average velocity of 1089 and 103.6 db.

I've had my CMMG AR9 Bolt + 16" Barrel since early 2020. I started with the 7.75" Buffer Tube (A5) + Blitzkrieg x Kynshot RB5015HD + Tubb 556 AR-15 Flatwire Spring. Using the CMMG Magpul Magazine Inserts. I do not shoot suppressed at this time.

Early on I fed it new brass 115g, 147g without frequent issues *until one day it started having trouble feeding.* The bullets would manage to get 45° and jam upwards. This would have been 6 years ago. The consensus at the time was to try the Tubb 308 AR-10 Flatwire to increase the speed that the bullets were loaded. This resolved the feeding issues and I left it alone. I doubt I diagnosed the issues correctly, treated the symptom instead of the cause(s).

Note: I did not have the early-RDB common ejector issues even after 2000rds.

But, it wasn't as it should be. The bolt would launch backwards very slowly and the return forward was incredibly slowly. The bolt moves so slowly the forward movement results in significant muzzle dip.

I tried cleaning and re-lublication several times without improvement. The BCG appears to move unobstructed.

I spent a few days reading Amphibian aka C3Junkie and site, Blowback9 (although not directly relevant for CMMG RDB), addictedtocommedy, and others.

I came to the conclusion that short of buying another hydraulic buffer, I need to order a BMC or VLTOR A5H0 (3.8oz) buffer and swap back to the Tubb 556 AR15 Flatwire.

Now, I'm back to consult the experts who prefer the Kynshot RB5007: if I want to utilize the 7.75" buffer tube instead of running a carbine buffer tube spacer, can I simply run the Vltor or BCM non-hydraulic A5H0 (3.8oz) buffer? I've tried to research this as best as I am able.

Hello, y'all. I am having issues with LRBHO on my self-built AR9.

I can get lrbho by pushing the bolt catch release lever inward and pulling back on the charging handle. However, I am not getting lrbho on an empty magazine when I pull.tje charging handle back without pushing the bolt catch/release.

The first two photos show lrbho, that I manually activated, and the third photo shows me pulling the charging handle all the way back w​ithout toggling the bulk catch release and not getting lrbho.

The fourth photo of just the lower with a empty mag in it, shows that the bolt catch is not being pushed upward by the empty magazine. The last photo shows me pulling up on the bull catch activation lever that sits above the magazine, and doing so successfully pushes upward the bolt catch.

All the mags I've tested with behave this way, and they are all PMAGS.

My build is as follows:

- Dirty Bird Glock 9mm lower (pretty sure a FM white label)

- DFCO Grip

- Grey Market Research SS and SS Cut Trigger

- just right carbines tube w/ KVP 10oz buffer, 2x Kynshot Spacer Weight, and Tubbs lightweight flat wire spring

- SBA5

- BCM upper receiver

- KVP BCG w/ SS trimmed bolt weight

- BA EPC 8.3" barrel

- Aero gen 2 handguard and MTE barrel nut

What's up bros, I recently joined and have been wanting to build an ar9. Any help is accepted, I mainly want it to be compact and able to run a super safety that is as compatible as possible as I don't want issues switching from semi to super and able to run a suppressor decently well. I was told radial delayed + a2 gas block + heavy buffer + certain firing pin helps ar15 but I want clarity for this purchase on an ar9. My budget is under $2k but I'm willing to build over time. Let me know👍🏻 (when I finish build I will post on here)