Powder vs Bullet manual

[simong]

Afternoon all,

Sorry if this is a bit of a “bone” question but…….

The Vhit data says 37.0grams of N140 to 44.2 but my sierra manual says 45.5 max
Is there a general rule of thumb as to whether the bulletin manual is more realistic or the powder one?
Obviously load would be worked up.

Ta muchly
The Greek

[spikedueller]

It's a common question and you'll likely receive a number of different answers, but in simple terms, you'll need to look at both sets of data more closely, what bullet, case, primer, firearm / test barrel is used in the Vit data compared to that in the Sierra, chances are they are not the same.

The bullet manufacturer data is a better choice if you are using the exact same bullet they are using. A lot of powder manufacturer data is for an x grain bullet of unspecified manufacture or type.

Bullets of the same weight but different manufacturer may have different bearing surfaces, jacket thickness and core hardness all of which can influence pressure and thus the loadings worked up and published.

Case capacity varies significantly between manufacturers so expect different velocities / powder charges.

Nothing in reloading is absolute so always start at the minimum load and try to duplicate as much as possible the load if specific components are listed. If not then you'll have to exercise your own judgement as to which data best matches what you have.
Finally don't be surprised if your velocity figures are different from the published data, look at the barrel length specified and if it's a test barrel as opposed to an actual firearm. Remember the loading data is produced and tested in laboratory conditions and may be very different from where you are testing them.

[1066]

Just a note there - don't get grams mixed up with grains, You might get a nasty surprise. :)

[Mattnall]

Also be aware that each source will give you figures of recipes they have tried, tested and found to be the case.

Different testers may find different values for min, max and never-exceed charges. All will have slightly different variables from chamber dimension to height above sea level at which testing took place.