I wouldn't call myself an expert on this, however, it seems to me that if the cartridge is getting longer when running it through the action, then the bullet is too loose in the case. I believe you said that you put a good deal of force on the bullet after you loaded the cartridge and it didn't move. It seems odd that a carbine action (unlike a bolt action with much more leverage) would be able to move the bullet. Are you sure you are taking uniform measurements with your calipers? Sometimes when I measure the overall length, I get inconsistent readings, depending on how I hold the cartridge in the calipers.
I load for four calibers - two handgun and two rifle, and I always use a separate crimp die, perhaps overkill, but it makes me more confident in my ammo.
One thing to think about is the case itself. I was having trouble resizing .30 Carbine brass with the Lee carbide sizing die. I had a couple cases get stuck in the die and had to hammer them out. I spoke to someone at Lee a couple times - their customer service over the phone is excellent (hope I am allowed to say that here, if not let me know, moderator) - and they explained that although the carbine case is similar to a straight walled pistol case (unlike a shouldered rifle case) it is different in that it has a taper from the head to the mouth. When sizing a straight walled case such as .45 auto or 9X19, the case passes through a ring - like thin doughnut - of carbide inside the die. So the case only contacts a small surface of carbide as it passes through. However, as the carbine case is tapered, it is forced into a carbide cone such that at the end of the press stroke, the entire case is in contact with the carbide surface. This is why case lube is recommended, even though most carbide dies do not require it.
Now this can cause a problem when you think about the fact that the dies (sizing, seating (if used for crimp), and crimp, size the outside of the case, however, the bullet is held in place by the inside of the case. If all cases had the same wall thicknesses, then that wouldn't be an issue. But they don't. So the dies have to be constructed to work with relatively thin and relatively thick walled cases. If you have a thin walled case, you will need to size more to achieve the same bullet tension. If you have a thick walled case, then sizing too much will risk getting the case stuck.
Sorry for the rambling. I have also loaded for .45 auto, .45 Colt, and .30-'06 and I find the carbine case to be the most challenging of all. These are some of the things I have learned as I have had more experience with this caliber.