Seating to crimp groove vs powder charge

[1hole]

That was the myth for many, many years. I believed it too because it sounds reasonable. Problem is, it doesn't work out that way in reality. I've spent a lot of time, effort and expense trying to determine, by actually measuring the pressures, that cast/lead bullets give less pressure with the same loads as does jacketed bullets of the same weight, seating depth and bearing surface. I've done this with numerous handgun and rifle cartridges. Best I have come up with as to which will give the greater pressure for a given load is; it depends. What exactly it "depends on" I haven't found a concrete answer for. Thus, based on actual pressure testing that theory is not provable.

If you have any empirical data based on the actual measurement of pressures demonstrating such, I would certainly appreciate seeing it.

Larry, you've mentioned your interesting pressure experiments several times in the past but I'm puzzled about how you did those tests. I mean, for handgun loads, did you only have a pressure test gun with short throats and tight chambered barrels for everything or did you have some kind of common real world long throat and cylinder gap barrels for revolver loads?

What I'm wondering about, might the very short throats of autoloader test barrels vs. the real world long throats and cylinder gaps of revolvers account for the significant pressure differences you found (or computed?) between shallow vs. deep seated revolver loads?

[Hi-Speed]

We're not going to get any "pressure signs" at 38 SPL pressure levels. If you do then you are probably above 357 Magnum pressure levels.

However, this is where the chronograph comes in handy. If you're using a different bullet than the manual, then drop back and work up to the same velocity level as the manual load. Not necessarily precisely accurate pressure wise but if all the other components, particularly the powder, then you'll still be within safe pressures.

Larry is spot on. This is my practice too and the chronograph is an indispensable tool for this. An example - using Speer 38 Spl +P load data their max load for the 158 gr SWC is 6.0 grs using Power Pistol. I start at 10% below and work up…I’ve had 5.6 grs Power Pistol come close to the Speer 6.0 grs Power Pistol manual load velocity in my revolvers as extrapolated for barrel length…stop there.