I trying to get the regulus and I went through the Iron Horse raid getting the first two-part from Lieutenant Grey and Captain Fieser but when getting past Major Williams and Colonel Morozova the parts that dropped from each encounter did not drop I would like to know why because it was my first run on normal this week
Hello @NZL-Squidy thanks for getting in touch with us about the Iron Horse raid.
The Engraved Muzzle required for the Regulus is a known issue we are investigating. A few other players came forward to let us know they did not receive any loot after killing these bosses. Sorry for any inconvenience caused because of this bug.
Hello @lynxgm6! Welcome to Discussions!
Sadly, we don't have an update at this time but I would like to get more information about this from you. Could you please let me know which parts dropped and the two that didn't drop for you? Please also try our troubleshooting guide here and verify your game files. Let me know if those steps helped or if you're still unable to get parts to drop. Thank you! 
@cptringsting @Disturbed0ne77 @CptRINGSTING Hey folks, apologies for the late response. Could you all confirm exactly which items aren't dropping for you, and which bosses you're defeating?
Hey @dopesoul007,
Thanks for reporting the two missing drops for you. The Engraved Muzzle and the Engraved Drum not dropping are already under investigation, like mentioned previously, and all new info about the investigation will be published in the News & Announcement section of the forums.
devtrackers.gg