Why the grain discrepancy?

[coondogger]

Same bullet, same powder, different starting load. For a .223, 45 gr Jacketed spitzer and H322, Lyman lists 24.5 grains for a starting load while Hogdon lists 23. Even stranger, the max loads differ. I’ve decided to follow Hogdon’s data, but what gives?

 

[cfullgraf]

Different techs doing the testing, different lawyers, different lots of powder, different atmospheric conditions, different test fixtures/firearms, different phases of the moon, different year the testing was done and so forth.

 

[CKweigand]

Ballistic lab conditions vary from differing sources conducting the testing procedure.

One technician might be using a universal receiver with a 1:7 twist

While another lab technician across the country is using a 223 action from larue tactical with a 1:8 twist.

Not saying this is 100% the answer but it happens more than you think and COULD be a contributing factor...

 

[Wreck-n-Crew]

Just to add sometimes the COAL. Especially on pistol rounds.

 

[ArchAngelCD]

Like said, conditions and equipment and even powder lot numbers differ in each testing lab.

I usually use a consensus of multiple sources when first setting up for loading a new cartridge/powder combination. I approach the upper end carefully and most times have no need to put to the top because an accurate load is found before I reach the limits.

 

[edwardware]

You didn't think those Max Charge numbers were absolute did you?

This illustrates why it's so funny to see people wrap themselves around precise conformance with charge or COAL data; ALL of that data is measured by someone, on some day, in some weather, in some test barrel, with some batch. . . and if you change any of those inputs you should expect to see at least a few % change in pressure.

The data is a guideline. Start low, and pay attention.

 

[Goneshoot'n]

Different techs doing the testing, different lawyers, different lots of powder, different atmospheric conditions, different test fixtures/firearms, different phases of the moon, different year the testing was done and so forth.

Emphasis on the different lawyers and techs! Last week I was a part of a weld audit for a very large assembly at work, 4 different weld inspectors bickered like children over what was ok and what was not, even though there was a clear, outlined standard in place. A fancy job title means nothing. Sorry for the rant, but I think that's got a lot to do with it

 

[Bfh_auto]

I use the lightest start load and the heaviest max load. Generally there is something good in between the two. I usually don't go off the reservation unless it's an old neutered cartridge in a newer action.