Regarding feeding, rather than extraction, something I've not mentioned before, but is applicable to ARs in general and especially so for the Solo:
One thing I've noticed, and it becomes even more apparent with these manually-operated actions, is that a lot of 223 bullets tend to stick in AR barrel extension feed ramp lug cuts. Not all bullets and not all extensions, but most in my experience.
The "pointier" and smaller diameter the bullet, the more it tends to jam into the bolt lug cuts, and stick a little (75ELDM, for example can lodge pretty tightly). AR dual feed ramps can be a lot tougher on a bullet than a bolt rifle with one large feed ramp.
A gasser has so much force upon chambering, it generally pushes right past this sticking point, but you'll notice gouges in the bullet from where it hung up on the ramp if you unchamber the cartridge, and this sticking probably increases the chances of bullet setback as well.
What I now do on all my 223 AR ramps is break the sharp edge on the lug cuts where the bullet is hanging up.
The simplest method I've found is to put the barrel in a paddled vice, wrap a small piece of 400 grit wet-dry sandpaper around the tip of the bullet in the cartridge and -gently- push the bullet through the ramp in its normal feeding orientation, straight into the lug cutouts, -only- making contact at the sticking point, not the ramp itself. I check frequently with the bare bullet to see how much the sticking has been reduced.
Once the bullet is moving through with little or no sticking, I finish with 1,000 grit. I'm not aggressive with it and it takes very little removal. You're really -just- breaking the sharp edges on the barrel extension ramps, where the bolt lugs pass, that are cutting into the bullet.
I've done this on my 223 straight-pulls and gassers and have never made feeding worse, only smoother and better. Sticking hasn't been an issue on 30 caliber bullets as they're wide enough not to enter into the bolt lug cuts. I don't how 6, 6.5 and 6.8 bullets move through the same, but probably easier as they get larger in diameter.