Decent case mouth flaring to start with?

Bullet seater, then bullet crimper dies, or just a combo seater/crimper die instead?

Does the bullet seating stem match the bullet tip type, hence not using a flat seating stem for a round noise bullet or the other way round?

Are you trying to over taper crimp the bullets, and why you are ending up with budge case at the rims?

Full boat in the shell holder when reloading, so the shell plate and tool head has equal tension all corners?

Also, short of using a M type case mouth flair die, or the M type powder through expander that will allow the bullet to sit square to the case when you set the bullet in the case/ as it enters the die, you have to hang onto the bullet to keep it square with the case as it enters the die instead.

As for case growth, yes with Starline brass, since your dies will size the case's smaller OD that how they where sized from Starline to begin with.  So with the cases OD sized smaller, this means that the brass will be slightly longer after such. You will not to trim the case, but will need to make the needed adjustments isntead.  Hence since the sized case will be slightly longer, will need to adjust your case mouth flairing tool so it not over flairing instead.

I load 9mm on a SDB.

Sometimes with matched headstamps, other times with mixed range pickup.

You don't mention the bullet type, weight  or shape.

First batch of bullets the same as the second batch?

If the bullet ogive varies, the OAL will vary as the bullet seater die indexes off the bullet ogive.

Bullet seateing die needs to be adjusted with cases in all stations, just like the sizing die, powder measure and crimp die.

9mm case is tapered, sizing die is not, so you get some bottle shapes.

As long a case gauges or "plunks" you are fine.

With a 115 gr RN, my CZ 85 will not chamber OAL's that exceed 1.10. (the OAL in Lyman 49)

But different chambers are different.

OAL's in manuals are a suggestion, you set OAL to your chambers.

For those who don't know, the SDB has separate dies for seating and crimping.

FYI, make sure that your bullet seating stem matches the bullet nose type you are reloading.

Flat tip bullet seating stem on the left, round nose bullet seating on the right.
https://www.dillonprecision.com/square-deal-b-individual-dies-parts_8_48_25288.html

You don't load for a CZ do you? Reread my post.