BehindBlueI's
Grandmaster
- Oct 3, 2012
- 25,897
- 113
SThe companies that publish these books use specialized equipment to measure pressure. They determine max loads because that load is the maximum that will stay under the safe pressure limit for a given cartridge.
Eh, not quite. Max charge/pressure is a compromise. One that's usually worth listening to, but keep in mind older manuals will often list higher charge maximums then newer manuals. You won't blow up a gun in good working order by exceeding max charge a bit, although you may very well reduce lifespan. Proof loads are normally some 25%-30% higher than max charge, and a firearm is expected to function with a proof load without damage. Also keep in mind that not every gun has the same capabilities, even if it shares a common cartridge. That's why we have +P, Ruger Only loads, etc and why some .45 Auto firearms will fire .45 Super without a barrel swap but others can't.
That's not to say you should ignore the books all willy-nilly, just keep in mind they aren't infallible or hard limits.