Despite what some think , handloading is not an exact science , just because the manual states that you can load ( x ) amount of ( x ) powder and get ( x ) FPS with ( x ) bullet and have ( x ) PSI or CUP does not mean that is what you will get in your firearm , the powder and bullet companies well be the first to admit that these are Averages . That is why they show SD ( standard deviation ) of FPS .
Over the years we have been told that there are certain things to look for as far as high & low pressure signs go , most of that info has been proved to be just maybes and conjecture , Granted some do hold true , for example if you open the bolt of a rifle and your primer falls out , it is a good indication that you are running way too high on your pressures , However just because you have a case that sticks or is hard to remove does not necessarily mean that you have a high pressure problem , it could be a simple case of you forgot to remove the sizing lube from the brass before you shot that round ( been there - done that ) .
Another example is when you seat a primer it feels diffrent from another , this could be explained in more than one way , not always because your pressures are too high , just switching brands or type of primers could also explain this . ( see chart )
http://www.jamescalhoon.com/primers_and_pressure.phpIf you were using say Federal 200 small rifle at a cup dia. of .1757 and then switched to Fed. 205M with a cup dia. of .1744 for a difference of .0013 , there is a chance that when you seat the 205M you will feel a difference in how much pressure you need to seat that primer .
Soot around the case mouth and neck has always been a good indcation of a low pressure round , just for the fact that the brass is not being pushed to completely fill the chamber and allows the gas to flow back around the case . so you can see that not always what we have been told is the only way to explain things .
Any time you change a component , be it bullet type or style , powder charge , case brand , primer brand or style , COL or Firearm , you are changing the numbers , so we as handloaders need to remember that the printed data is a guide not an exact . Another thing that we need to do is cross check the info that we use , not always is the data given the same from source to source .
So please use common sense and remember to double check all data you use .
Richard
