The products in question were Foxtrot Mike 5" FM45 uppers, purchased three of them, purchase was based on prior experience with a 16" FM 45 upper which feed flawlessly, however Foxtrot mike has changed the profile of the feed ramp / barrel throating, which now cause 75% of factory 45acp 230 FMJ ammo to wedge itself at a 45 degree angle in the barrel throat.
I contacted Foxtrot mike for trouble shooting help as the FM45 products come with a FM9 manual which specifies which 9mm ammo to use but absolutely no 45acp info. After multiple back and forths with FM I replaced the buffer to their FM45 buffer, already had all the other factory parts, even switched back to Glock factory G21 magazines as they don't recommend any after market high capacity magazines (heaven forbid we might want to use a magazine larger than 13rnds in an AR15 type rifle) Long story short, still exceptionally unreliable with only the occasional round feeding. Ended up having to dissemble all three uppers to properly throat the barrels to get even 90% reliability, relegating these firearms to range toys only.
With all that being said, the only two feedbacks on your website from 2020 say how reliable the uppers were out of the box. hence my desire to shed light on FM products change in product specs and resultant reduction of reliability or even usability.