Pressure question

[leo158]

I am sorry about all the questions on here? But here is another one. And i do thank you all for your help with me being new to reloading. So here is my question. Do I want loads that keep my pressure down or how is that played?
Again On this RL website http://data.hodgdon.com/cartridge_load.asp It is showing for the 55 gr bullet 22-250 around same FPS on alot of rounds but the pressures are not consistent. I would like to keep my FPS around 3600. And what is cup compared to PSI. Thank You all again, Dan

[308law]

Questions are the only way to learn, so no need to apologize. A lot of the time loads will be the most accurate at or near max pressure but not always, I wouldn't worry too much about the pressure rating in the reloading manual that much, just don't exceed there max load and watch for pressure signs as you approach max load. The difference in the pressure between multiple powders is a sign of their burn rates. The 22-250 is a barrel burner and will last longer if used at lower pressures, but that is more like starting loads or just above starting loads vs maximum loads. The difference in barrel life between two powders with a slightly different pressure at max load would be minimal. PSI is pounds per square inch and cup is copper units of pressure. Cup is the old way of measuring pressure, a pressure barrel with a mechanical device that measured the amount of "crush" of a piece of copper after firing. Psi is a newer way with an electric transducer that measures pressure. These are very crude explanation but I hope this helps, there are whole books written about pressure.