It is imperative with semi-auto handloads that the bullet not set back in feeding. Poor functioning and accuracy can result, and possibly even high pressure, creating a hazard. Some factory ammo actually has a crimp in the case just below the bullet base to help prevent setback.
Make sure the case tightly grips the bullet. The expander plug should be no more than .351" dia for a 9mm, and smaller does not hurt. Yes, you see a slight step in the case below the bullet, which some find unsightly, but that step is one of the features that prevents setback.
As others have noted, a firm taper crimp is required, but the crimp alone cannot replace the tight fit. You want both.
I like to use either an RCBS or Redding carbide sizer, then a modified expander plug die, then seat in a Redding Competition Seating Die (spendy) then finish with either a RCBS or Redding taper crimp die.
Lots of bullets & powder work well in the 9mm. I'd lean toward Titegroup for mild loads, and AA#7 or Power Pistol for warmish defensive loads.
I noticed recently Speer's 124gr Gold Dots are starting to be in stock at stores. That's probably the best bullet for defensive use available to reloaders.
Good Luck!
