After changing a number of components, the rifle appears to be working properly again. The items that were changed include:
Swap from AR-15 collapsible stock tube to Vltor AR-10 collapsible stock tube
Replacement of cutdown aluminum buffer body containing two tungsten weights (weighing 3.8oz) with steel buffer body containing two tungsten and one steel weights, resulting in a weight of 7oz.
Replacement of stock short action spring with Tubb CS flat wire spring
Addition of o-ring on extractor spring.
Individually, these changes only reduced the number of malfunctions; all were required to (seemingly) eliminate them.
Very observant viewers may notice a little bolt bounce; this may be reduced with the replacement of the one steel weight with yet another tungsten weight, but I’ll be doing more testing to see how reliable it is before I say for sure that that’s the setup I want to use. I’m more concerned with consistent extraction and ejection at the moment, and high speed video seems to show that the weapon is working properly in that regard.
The video is pretty boring, but here it is: