If at any time any anomalous behavior is observed, STOP.
Check EVERYTHING.
Do NOT move forward until the process, components, and testing equipment are confirmed.
Chrono-mapping: Add powder in .2g increments, chrono plenty, and as you work upward in charge weight you hope to observe a similarly progressive increase in fps.
Usually you will.
But, as queried, what if you see a sudden spike in velocity (fact: it can spike in either direction)?
I personally continue, as I have learned that the loads can return to a progressive increase.
To all following this thread, the OP has a
specific goal for his load; he would like a defense-capable load for bear up to 600lb.
So, consider goal during the development process.
Based on goal, the .430" 275g bullet will need at least 980fps to provide sufficient penetration, and more velocity will aide further penetration.
Too much velocity may damage the bullet on impact, or during penetration, reducing its ability to penetrate further.
The specific bullet chosen is tough.
Since the final load will not be fired by machine, its recoil signature literally affects its effectiveness. The load must offer controllable accuracy, which is directly at odds with ever-increasing recoil as the velocity increases.
The platform used is tough.
That is not to suggest it is indestructible (I bent my 5.5" 44 Redhawk using a 300g lead bullet and poor loading process).
Starting will be easy.
With no published data for the specific combination, extrapolate a start load by using data for similar bullets --in this case hard-cast lead-- that weigh more and less.
Start.
Test.
Recoil will be a prominent factor during development; it will allow you to decide what more velocity may mean regarding controllability.
Maintaining controllability, work upward. Slowly.
The powder chosen has a progressive nature.
That does not automatically render every load safe. Testing in the specific platform will give data on its nature through the specific platform.
I promise: A 275g .430" bullet, regardless of velocity, means recoil. How much?
Personal in feel, and shooting results.
Vihta's data offers a 267g lead bullet, close to the chosen 275g lead.
They also show 300g data for two jacketed bullets.
Take all three start loads, and use (in this case) the lowest, since they are all close.
The bullet will not stick in the bore.
Work up in .2g increments, making five to test. Chrono, consider, add, test, observe.
Maintaining progressive behavior, and permitting controllability?
Since the goal will be readily met with velocity in the 1100--1200fps range, stop when you're satisfied.
Then make more, and test.
Still good?
Make many more and test; test in varied environmental contitions.
Still good?
Yer done
