Recently went to the range with patched boolits seated in Minimum tolerance trimmed brass. The patched boolits were measured to chamber and throat. I ended up with cartridges that cut paper rings one after the other. (Certainly was depressing to say the least.)
So it (does) matter how long the brass is. To stop my rifles ring cutting. I had a few (new) 32 Special brass that I resized to 30-30 diameter. Then measured their necks and ever so lightly trimmed to eliminate near all its forward unused clearance. What a difference. No ring problem what-so-ever. So my conclusion is: New or first fires that haven't been trimmed is a necessity and have to be properly trimmed to chamber tolerance as close as possible. {thus having a cast of the chamber and slightly froward of that even showing some rifling would be handy to have as a reference tool.} As you can see in the (link) a necks unused open area just prior to the barrels throat. That little 2 or 3 thousandths open area no doubt does influence a patch's behavior. The heat and pressure filling in that little space must be tremendous pushing up against a boolit patch.

https://www.google.com/search?q=30-3...l%3B2607%3B661