Decided to order the 25# springs at the same time I ordered a couple different bolt knobs to try. ARC emailed me a tracking number within 90 minutes, so it appears they are trying to stay on top of things at the shop.
I have to say, the long barbell is extremely comfy... but so is the egg. I think I prefer the long barbell because it provides a nice finger groove to lift the bolt with the side of your index finger just like the stock knob. I may pick up a short barbell to try too, I didn't realize the long barbell was so much longer than the stock bolt knob.
I also tried the 25# spring... it's a bit fun to hang onto the washer while trying to compress the spring and start the castle nut without launching everything into the ceiling. The 25# springs makes a very noticable difference in bolt lift compared to the 19# spring, but it's still not terrible IMO... especially with the long barbell knob since it gives you more leverage.
Since my 223AI is still running great with the 19# spring I'll stick with it for the lighter bolt lift but keep the 25# spring in my range bag just in case. I'd like to see a 22# spring offered too, perhaps in conjunction with a lightened firing pin and cocking piece...
It would be nice to see a status update from ARC regarding the availability of the redesigned bolt heads and the knurled firing pin tool.
At some point I'd like to feel a Nucleus with the 25# spring right next to an Archimedes with the 25# spring to compare them.