Suggestions and comments are most welcome.
1. Did you make sure you thoroughly removed all the copper from your bore before you shot any lead? And I don't mean running a patch with Hoppe's #9 through it. I am talking about using a copper removing solvent until the patches have no blue on them.
2. I suggest you use a mid burn rate powder. Then select a load that starts at the pressure that Missouri Bullets recommends for the BHN of the bullet you are using. And keep in mind how sensitive the 9mm is to bullet seating depth and how critical it is that you use the same seating depth as the bullet listed in the manual. You can use this link
to compare bullet lengths. It isn't the OAL that is critical, it is the bullet seating depth that determines the pressure.
3. Adjust from there.
I would think you have a problem currently with using too fast a powder and loading it to too low a pressure. You also might have a fit problem, but at least give the bullets a chance.
And the last thing you should do is shoot a jacketed round through a barrel with heavy (or any) lead deposits.
Soaking the barrel in Ed's Red or Kroil will make the lead come out much easier. But if you are getting that much lead after 50 rounds, you have major adjustments to make.