It does run- the other day I burned through 300 rounds as fast as I could reload and pull the trigger. The only failure was a bad Bulgarian primer that refused to do its duty.
I was also surprised that it did not need the tube to keep the carrier in alignment, but another reason for the long buffer is that the piston never exits the rear sight base. The carrier runs pretty straight and a slight chamfer on the front of the piston is all that seems to be needed to keep things running smoothly.
I don't have any problem with split cases, bulges, or even dings (except of course for the Bulgarian and Polish surplus, which was thoughtfully pre-split for us). Cutting the chamber is a critical operation, as you know, particularly when your trying to close down the gap between bolt face and breach as much as possible without compromising extraction reliability. I also found that I needed to throat the chamber slighty- I noticed that sometimes when I tried to extract live Bulgarian rounds, the bullet would stick in the throat, and with those split necks, the bullet would be pulled out of the case and be left in the throat of the chamber-messy...