A lot of great advice has been given.
Let's talk about pressure. Guns are designed in some kind of a fatigue plus pressure vessel for human use methodology. This is tricky because if both methods are directly combined, the factor of safety becomes so high that you could not carry the guns around. There is also a historical perspective in firearms design where guns were made before much of the engineering science was less complete than today.
All I am saying is a single overload of moderate pressure increase is not going to blow your gun up, but it still may be too hot.
Gun blow ups are often related to multiple factors between unsuitable ammo, too clean or too dirty bore, mechanical issues with the gun, etc. I guess I'm saying if you run a 75000 psi load down your bore of a bolt gun, that alone won't damage your gun. That with a crack case head or clogged bore could damage your gun.
When you reload, be very careful to inspect for case condition, a crack in the case creates a high pressure jet of gas like a cutting torch. Bad for the gun and bad for the shooter.
Always match primers to the case type and load data.
Powder selection is a bit trickier. Powder selection is basically set by burn rate, but trying to guess a powder often puts you outside manual recommendations….why? Manuals select powders based on burn rate, pressure development characteristics, and stability. All 3 are super important and you cannot see stability very clearly without shooting.
A manual will never put you in too bad of a powder.
So, learn pressure signs, shoot ladders from min to max in the manual. Find that pressure sign and back off about 1-2%.
One benefit of working in this area of the load spectrum is high pressure safe loads can be very accurate and very stable. Notice I say high pressure, not over max pressure.
So how do I manage this…
Plan your load. Study all the data you have for what powders are available, what you may have, what provides velocity you want, what is temp stable, etc.
Load your plan. Take notes on each step including target measurements and samples of actual. Setup your process and throw some test charges before making your keepers. Have one powder on the bench, as many have said. Label what's in the measure. Write down your target charge weight and range…..no, you don't have to do all this….you have to develop a system that works and allows you to stay on task. Make sure your scale is truly capable. Mechanical scales get dirty/dusty which greatly affects their reliability.
Check your load. Look for velocity at or below book value when adjusted for barrel length. Look for pressure signs. Look for large group accuracy. Look for good <20 sd.
- don't mix up pistol and rifle powder (moot, as I won't be loading pistol)
Good point, but I would clarify….you need to know exactly what powder is in the manual, transferred to your plan and loaded into your process. There are really no acceptable errors in powder selection for loading, even if you and the gun survive.
-have a system for making sure you don't "double-load" (although it seems like if you double-loaded a rifle cartridge it would overfill and spill all over the place)
Good point.
Why would calipers be a safety thing? I do have a good one, just wondering.
Calipers help you control oal. OAL impacts start pressures, which can impact max pressures and the pressure duration.