Measuring the case length identifies this problem. Trimming the neck is the solution. The shoulder does not need to be pushed back.
I understand that the same thing can happen as you said, with the cases being too long, but that wasn't the issue in my case. I can trim the cases to the proper length, but if the shoulder is to far forward the pressure issue persists. I didn't mention it before, because it wasn't what the problem was, but my friend did check the case length. He was thinking exactly what your saying.
This is a problem that should have never been if proper measuring had been done. The fact that it was spotted by a chronograph was a happy and lucky event. Experienced loaders always measure and trim as required, and would almost certainly have spotted the normal pressure signs without using a chronograph.
A good reloader may have spotted the issue in time, but the chrony revealed it very quickly.
The issue was explained to me by a very good gunsmith. And his explanation was easily proven to be true by measuring the headspace with either the headspace comparator or the precision mic. Both tools take a measurement from the head to a datum point on the shoulder, not the case mouth.
Considering that tools such as the precision mic, and the headspace comparator were developed makes it obvious to me that I'm not the first to have such an issue. And using these tools, not my trimmer, has resolved the issue years ago.
The thing that I take from this is to make sure that when you ask someone to help you learn to reload that they actually know something about it.
Umm... Ya might want to think about it before you make such a comment... I had an issue that you've obviously never dealt with, or maybe never figured out... My gunsmith immediately figured out the issue. And what he thought it was, was immediately proven with the tools I've mentioned. As I said above, the issue was also resolved as a result.
I have been using chronographs for many years. They are a valuable tool for measuring velocity and SD, but they are absolutely not necessary for a beginner that is trying to put together a reasonable kit for $250.
Never said that... Just stated that I'll always us one, and why.