I did not read all of this but.....If you work up a load.... fire one and get the case. Then look at your primer. If it has flattened meaning the bevel around the primer looks different then when it was first loaded do not keep shooting these rounds. Use your bullet puller remove the bullet and powder then fire the empty case to blow the primer. When you see primer flattening you are about to make things go boom. Google this for more information.
While this sounds like good advice it is outdated and mostly incorrect.
Back in the olden days, I'm talking the 50's and 60's before home chronographs were invented and before there was a lot of load data about, this was standard advice. In today's world it ain't. There are lots of loads, especially in rifles that will lead to a flattened primer. It does not mean the load was excessive. There are other case criteria you can look at depending on what kind of case you are using to help determine if the load is too hot. In all fairness the case condition is far too crude and rude to be a proper gauge of the load. There are too many variables in the case such as brittleness of the case, size of the primer pocket as well as primer itself for a couple to be a reliable indicator.
On the other hand if you have a case where the primer is severely deformed, falls out of the primer pocket, show signs of gas escaping around the primer or has a crack around the case forward of the head of the case, is difficult to remove from the chamber, stop shooting those loads and find out what the load consists of and check it against the load manual. Of course that still won't tell you if the problem is a magnum primer in a load where a standard was called for and the magnum peaked pressure outside of normal parameters. You can't tell a magnum primer from standard by looking at it. They are identical in appearance.
Lots of handloaders get into trouble because they think that factory ammo and the loading manuals are set with data that is too conservative. Hogwash. While the factory does have to set loads that are supposed to be safe in many different brands of firearms they ain't piddling along unless you are getting reduced velocity loads.
The loading manuals were set up using proper pressure barrels and determined by the use of proper and dedicated pressure equipment. Those loads are set to a SAAMI standard, the same kind of standard the gun manufacturers use to make the barrels, chambers and receivers to. Yeah you might be able to gain a couple hundred FPS in any given load but without a pressure system on your gun you have no idea if you took a good standard load from the max pressure of say 55,000 CUP to over 70,000 CUP or far more and risk blowing a fine gun up. Not to mention all the soft fleshy matter next the gun like your soft head. Trying to shoot what amounts to a proof load will not do you, the gun or the folks near you any good.
As I stated before, the max velocity load is rarely the most accurate and certainly not the most economical. To get that last couple hundred FPS you may have to add an exceptional amount of powder as case and powder efficiency are not static. There is a point of diminishing returns where more powder does not equal an equivalent increase in velocity. It most often equals a very slight increase in velocity at the expense of considerable hazard and shortened component and gun life. I have found better accuracy in mid range loads and can get more shots per case, pound of powder and gun than by trying to make the gun into a projectile flame thrower. Your cost per round goes up the more powder you use, especially if you only get one or two loads out of each case instead of 8 to 15.
If you think you know better than the engineers, physicists, ballisticians and chemists who put the stuff together, then you are in the wrong hobby and I damn sure don't want you next to me on the range. There are ballisticians who study this stuff for a lifetime and none of them will tell you they know it all.
One last thing. The reason I said it was a good idea to have multiple manuals is because sometimes they do make a mistake. My first manual had a load for a 38 special using a very fast powder, Bullseye, that was not safe. I fired 6 rounds, it sounded like a magnum and I had to pound the cases out with a rod. Another manual showed a 357 magnum max load with less of that powder in it. Fortunately I was shooting a very heavy 357 pistol built on a 44 frame and cylinder to it did not damage the gun but I pulled every load and redid them. I threw away the cases I fired.
