... What Gregintenn said and/OR...
The base of the bullet is NOT fitting into the mouth of the case thus, as you lower the ram on your reloading press, the bottom of the bullet is refusing to "start" in... and fit into the case's open mouth and thus the bottom of the bullet is crushing the whole cartridge's neck "down" yielding the "problem" you're having and why the second case looks as it does.
However, if this is the reason, then I'd expect that part of the edge of the case-mouth would very likely be bend over... either inwardly or outwardly where the bullet's base touched the case's mouth and refused to slide into it.
While I believe it's been previously mentioned, it also could be that you've got either the resizing die or the bullet-seating die screwed down much too far and the die is crushing down the case's neck and driving it down into the case's powder chamber. I say this because it appears in the 2nd. picture of the case, your case's shoulder has practically disappeared.
To determine this... simply LOOK at the case's neck and shoulder after resizing it and before attempting to seat the bullet in the case. I.E., does the shoulder look like the 2nd. picture
BEFORE or
AFTER you attempt to seat the bullet.
I.E., the case's "shoulder" has practically disappeared because the whole case-neck has apparently been driven down because either the die is set too low or the base of the bullet you're attempting to put into the case's open "mouth" refuses to slide into the open case-mouth.
This could be caused by your resizing die's expander-button NOT opening up the case-mouth far enough... or I suppose it is possible that your expander button doesn't have a large enough outside diameter. However, RCBS makes excellent and very "precision" dies, so I question that it's the expander-button's fault.
At least, these are my "guesses" from the
new information you just posted.
Jus' my 2�... 'cause I've run out of ideas.
Strength & Honor...
Ron T.