First build complete without any significant fitment or function issues (aside from a terrible locking block that P80 replaced without question). Slide went on like a dream and the barrel went in with no fitment required whatsoever. It's been fired into a can and it cycled perfectly. Very, very happy.
Prior to this project, my only experience with Glocks was picking them up in the LGS and deciding that they didn't fit my hand. Thanks to this community I was able to pull this off and had a blast doing it. I can't imagine how this would have gone if I didn't have access to this forum, the FB group, and MGB's videos. This community is just awesome.
I took the completed pistol into a local gun shop and had a guy that I trust look it over. Due to my lack of experience with Glocks, I thought a second set of eyes on it wouldn't be a bad idea. He used the word "perfect" to describe cruciform engagement, had great praise for the slide, and over all thought it looked great. He said it was the nicest of the 80% pistols he's seen -- and he's not known for handing out praise. Thanks, MGB!
Here's the build:
OEM lower parts kit with Gen 4 ejector
OEM slide parts kit
Zaffiri Precision 3v2 slide
Zaffiri Precision threaded barrel
Holosun 507Cv2 RDS
All OEM parts polished within an inch of their lives.