Reloading Notes - Part 1 (Sizing)

[Land Owner]

There is "so much" left unsaid or that is incomplete in the Missouri Bullet Company discussion with regard to barrel leading and the "formula" for hardness. You CANNOT simply hang your hat on those statements and those alone or that formula for the following reasons:

ONE.)

the purpose of generating pressure in the cartridge case is to force the bullet out of the case mouth and on down the barrel

says nothing of the sympathetic harmonics of a steel barrel and the powder pressure spike. The bore, a tube, expands and contracts as high frequency waves cascade from chamber to muzzle and back. We try to get the right boolit "fit" to the bore, the right lube, and the right powder charge for a specific hardness to place the boolit at precisely the height or depth (idk which) of a pressure node as it leaves the barrel. The last thing that touches the boolit is the muzzle.

TWO.)

Properly obturated, the base will have expanded beyond its original diameter which has the effect of “sealing the bore” against the explosive pressure of the gases burning behind it. Properly sealed, and working in conjunction with the lubricant in the lube groove, the bullet will thus not allow gases to escape forward from around the base of the bullets, which prevents it from shaving lead from the bullet body and forcing it into the bore grooves (otherwise known as “leading”.)

Gas cutting happens from the moment of hot gas ignition, as the case is slammed hard against the chamber walls, and before the boolit has overcome its own inertia against forward movement. When the boolit is forced into the lands and grooves there is a momentary rise in both resistance and hot gas pressure, obturating the base, and forcing the boolit into the bore.

TWO A.) You can push boolits too fast and strip lead by shearing.

TWO B.) Stress concentrations in screwing the barrel to the receiver and irregularities in the bore can strip lead.

THREE.)

The PSI of your reloads is published in the reloading manuals.

It absolutely IS NOT! The PSI of their TEST CHAMBER and BARREL is in their reloading manuals. All you have is an educated GUESS, close to the pin, with regard to your barrel and chamber pressure.

FOUR.)

For this application – shooting a 200-grain LSWC at 900 FPS requires that you use a bullet with a BHN of 16 to 18 (round upwards a couple of BHN points for flexibility.)

That "exact science" is TOTALLY out the window and leaves the reader to pick and choose something from 16 to 20 BHN. Real exact there...like 16 places to the right of the decimal point - NOT.

There is nothing wrong with experimentation. It is what we do. We experiment with a.) case prep, b.) primer, c.) powder, d.) mold, e.) boolit embedment, f.) jump to lands, g.) grip, h.) lube, i.) boolit sizing, and j.) alloy hardness, to name a few.

Leading does not go away because we calculate alloy hardness from a formula.

[Mint]

There is "so much" left unsaid or that is incomplete in the Missouri Bullet Company discussion with regard to barrel leading and the "formula" for hardness. You CANNOT simply hang your hat on those statements and those alone or that formula for the following reasons:

ONE.)
says nothing of the sympathetic harmonics of a steel barrel and the powder pressure spike. The bore, a tube, expands and contracts as high frequency waves cascade from chamber to muzzle and back. We try to get the right boolit "fit" to the bore, the right lube, and the right powder charge for a specific hardness to place the boolit at precisely the height or depth (idk which) of a pressure node as it leaves the barrel. The last thing that touches the boolit is the muzzle.

TWO.)
Gas cutting happens from the moment of hot gas ignition, as the case is slammed hard against the chamber walls, and before the boolit has overcome its own inertia against forward movement. When the boolit is forced into the lands and grooves there is a momentary rise in both resistance and hot gas pressure, obturating the base, and forcing the boolit into the bore.

TWO A.) You can push boolits too fast and strip lead by shearing.

TWO B.) Stress concentrations in screwing the barrel to the receiver and irregularities in the bore can strip lead.

THREE.)
It absolutely IS NOT! The PSI of their TEST CHAMBER and BARREL is in their reloading manuals. All you have is an educated GUESS, close to the pin, with regard to your barrel and chamber pressure.

FOUR.)
That "exact science" is TOTALLY out the window and leaves the reader to pick and choose something from 16 to 20 BHN. Real exact there...like 16 places to the right of the decimal point - NOT.

There is nothing wrong with experimentation. It is what we do. We experiment with a.) case prep, b.) primer, c.) powder, d.) mold, e.) boolit embedment, f.) jump to lands, g.) grip, h.) lube, i.) boolit sizing, and j.) alloy hardness, to name a few.

Leading does not go away because we calculate alloy hardness from a formula.

These are the posts I come here for

So I suppose the simple question is, is there a sort of generic way to know which hardness I need, that is more general at the expense of being super accurate? Ie, based on the principle that an educated guess is better than a random guess?

I ask because of all the BHN's available when I buy bullets. Up until now I have only bought 16, and shoot them at 900 - 1200 fps

[Bazoo]

I’d go 12 bhn for all your needs. If I’m not mistaken Missouri offers 12 and 18. But a 12 bhn is better balanced to lower pressure up to 357 and 44 magnum. A 18 bhn would be closer to what’s needed for 454 and up.