Originally Posted by jdwmyr
When seating bullets out further then the C.O.A.L how do you know how much more powder to add without going over pressure
To answer your question there is no set rule saying if you move the bullet this far you can add this much powder and stay within limits so.......
This is just an example of what kinda goes on.
In Quick Load.
27 inch barrel
70gr IMR 7828
Velocity 2916 fps
Chamber Pressure 60,751 psi (Max pressure 62,366 psi)
If you move the bullet out to a COAL of 3.600 the chamber pressure drops to 53,076 with a velocity of 2824 fps with all the settings above. You bump the powder to 72.8gr's, chamber pressure 60,340 psi with a velocity of 2936 fps your about back where you were. There are other factors here that effect chamber pressure (jump to lands etc.) and things that effect accuracy so take all of this with a grain of salt am just trying to keep it simple.
What is important is the ability to move the bullet around in and out to find the most accurate jump safely and maintain a decent velocity.
Loading manuals give you the data that they found using the listed COAL and you should not load any hotter then what they list as max with that COAL and bullet. The second you change the COAL the reloading numbers no longer apply accurately. There are other important factors evolved and every rifle is different and one should not leave the guidance of the loading manuals until enough experience has been gained with the proper tools to do so safely. Always when making a change in seating depth drop back a couple grains and come back up and the same practice should apply when using the manuals COAL and working up to a max load. Learn to recognize pressure signs which is always not a sure bet shoot through a chronograph and pay attention to the feel of the rifle when working up near a max.