I had the same setup, same issues. Buy a sprinco heavy spring and a Spikes ST-T2 buffer. It will then run just fine. Don't do anything else until you do these things. It really makes me wonder what RRA ships in their complete rifles.
Mine had the hardest time with 147gr bullets. 115 and 124 ran fine after the changes. I still haven't gone back to the heavy subs to see if they run. The fucker is a bullet hose now. 6 mags will spray out like a paint gun.
In the height of the ammo crisis, I am sure the guys at the range thought I was pure crazy. I would just show up, spray out 6 mags in a couple minutes and leave.
My fail to eject was really mangling my brass. The jams were hideous. The bolt was simply cycling too fast the cases would not eject properly.
Adco ramped my bolt and shortened the barrel to 10.5" before I started on this project. I used the mag block RRA ships and started out with Uzi mags. I learned that the bolt hold open was a good feature and changed to Metalforms. Now the Uzi mags are collecting dust.