Best way is to stick with known loads out of a loading manual. Always start 10% below max and work up, because as stated above, different components and guns act differently. For example, a 150 grain homogeneous bullet, like a Barnes solid copper will have longer bearing surface and be a little less compressible then a 150 grain cup and core bullet, and will usually exhibit higher pressure if you are using data tested with a conventional bullet. A tight bore is another example.
An accurate chrono can help. Velocity and pressure go hand in hand, so if a book load shows say 2500 fps out of a 24 inch barrel, but in your gun is chronoing 2800 fps out of a 22 inch barrel, then all else being equal, you are operating at a higher pressure.
Traditional signs of high pressure like flattened primers, loose primer pockets, sticky extraction, case failure, etc. can help, but are not reliable, as other factors like a rough chamber, headspace, bad firing pin, etc. could also be the cause. Again, when you reach loads that exhibit these signs that are pressure related, and not the gun, you are already too hot. Probably the most reliable indicator of high pressure for the the reloader is by checking case head expansion. To much to go into detail here, but their are excellent articles available to reloaders on how to do this properly.
I always wondered why Oehler stoped making the transducer based chrono system that allowed pressure testing. Maybe too many reloaders used it improperly and ended up blowing themselves up?
Larry
