Start with the basics:
- Do you have what you need to measure from the case base to the shoulder?
- Do you have what you need to measure from the case base to the bullet ogive?
I'm guessing from your post that the answer is no since you only talk about measuring OAL. OAL in a vacuum is all but worthless - in fact, I can't remember the last time I measured this.
Key questions you need to answer before you can safely and effectively load:
- What is the measurement of base-to-ogive when your bullet is seated at the lands? - this gives you your 0.000" seating depth - there are a number of ways to determine this. I use the Loctite method and found it to be the easiest and most consistent - and it leaves you with a physical record of a given point in time in your barrel life.
- What is the measurement of base-to-ogive when you have seated a bullet you intend to load? - if the number is greater than the above measurement, you are jamming the bullet into the lands - if it's less, you are jumping to the lands. If you are jamming, this would be a reason for the effects you're seeing.
- What is the measurement of base-to-shoulder of a fired, but not sized case? - this essentially gives you your chamber dimension
- What is the measurement of base-to-shoulder of a sized case? - this should measure in the neighborhood of -0.002" from than that of a fired, unsized case. If it's greater, this would be a reason for the effects you're seeing.
How could a case get sized greater? If you're die is set such that you're sizing the body, but not engaging the shoulder, the brass getting squeezed in the body has only two places to go: into the void left between the shoulder and die or into the open area above the neck. The path of least resistance is into the shoulder void - hence, it grows there.
TLDR: get the devices necessary to measure base to shoulder and base to bullet ogive. They are cheap and easy to use. Without them and the measurements they enable, you are likely producing less than optimal ammo and could actually produce dangerous ammo from too much headspace.