Okay, I re-tensioned the drum spring a few different times until I got a consistent feed from the drum. It now feeds almost 100%
Next issue I have is one that is not even remotely related to the drum itself. I bought a 1k round box of cast lead bullets from Wideners.com a while back. When I got around to loading these, I noticed that they chambered a little tight in my XD pistol. I've shot a handful of these reloads and noticed a few were difficult to extract. Well, although they would strip out of the drum/mag assembly, I kept having issues with them extracting. I had to remove several with a brass rod from the muzzle end. So, I loaded the drum up with only Remington and WWB factory rounds, and so far, the drum will feed all 72 rounds just fine. It's still a little finicky due to a few snags inside the drum, but I will disassemble the drum and media blast it soon.
Another issue I had was the feed ramp and bolt face. I haven't cleaned this rifle in over a year, so after having numerous issues with my reloads, I disassembled the bolt and set about cleaning the feed ramp and chamber. There was A LOT of gunk in there. I scrubbed and scrubbed with some CLP and other solvents in conjunction with a bronze brush. Turns out there was a lot of crap under the extractor claws as well.
So, now the rifle is clean and gunk free, and I have cycled about 210 rounds of factory ammo by hand with no issues.
Maybe I can take it to the range soon!