Still new to reloading and running into some issues.

Using a Dillon Carbide .223 resizing die, and when seating my last run of 55gr Hornady FMJBT, I noticed that I could push the bullet back into the case by pressing it against the bench. Was not able to do this with earlier runs (using Privi, Fed, LC Brass) but now that I've moved on to the S&B and Fiocci brass, this is a consistent issue. Played around with several expander ball depths with out any positive results (ball measures .223), and finally pulled the ball assembly all together. This is giving me .240 OD, and my seated bullet OD is between .243-.245.

My questions:
1. Any issues that you can see running the die without the expander? I decap on a lee universal decapping die and then wet tumble.

2. Is it common to have these issues switching between brass types?

3. Is there a possibility of this set up giving me too much neck tension and causing pressure issues?

Thank you all for your help, I greatly appreciate it!