Great posts. 14 years ago I had blown primer & case failure from a 243 with Barnes X bullets set too close to the rifling.

Here are a few thumb rules that I stick to now....

1. Never try to exceed the pressure tested max velocity for a particular powder / bullet combination. Yes you may need a grain or two more OR LESS to reach that published & pressure tested velocity. With due respect to experienced members on this site & elsewhere, I am skeptical of those who claim that their safe loads give them higher velocities in their rifle. That is contrary to the laws of Physics.
2. Maximum velocity for a load = maximum pressure (NOT maximum powder charge)
3. BUT - Maximum pressure may be reached before maximum velocity in a particular rifle - stop there!
3. For hunting loads, seat bullets 0.030 off the rifling & for mono-metal (Barnes X etc) make that 0.050 off the rifling.
4. For small cases like 222 Rem - do not try to go to 50,000 psi (you will blow primers like I did). The case is designed for 45,000 psi - I do not understand why this so low when the 270 can go to 62,000 psi. Again stick to max pressure tested velocity for load.
5. In rimless / smooth sided cases like 30'06, WSM, 308 etc, anything less than 10 reloads means the charges are too high & unsafe.
6. If reseated primers are not really tight (almost like a new case) then the primer pocket has expanded due to an unsafe load or the brass is too soft & needs to be scrapped. Yes - I have had lose primer seating in my 280 Ackley Imp with loads that did not get to max velocities! I just changed to a slower powder & bingo! I got the 3100 fps with 150grs bullets & 12 reloads out of the new brass.
7. Always check case length & trim if necessary. Stretched cases can pinch the bullet at the throat & pressure spikes to unsafe levels.

Yes, I know that some of those thumb rules may not be scientifically proven - but they are SAFE. That is why they are thumb rules!

Safe shooting to everyone.