For all those Reloading Manual Data Variance Questions

[BlackRam]

There has been a lot of discussion in various threads regarding the variances in the data from one source to another; whether in reloading manuals, or online data.
I just picked up the latest issue of Guns & Ammo, and there is an article in it by Dave Emary titled "Data Confusion".
Hopefully, the article will help explain the many reasons why there is such variances in the data for a given bullet/cartridge combination from source to source, for many of the questions out there on this today.
In the article he discusses the following factors:
1 - Pressure
2 - Bullet Design and Seating Depth
3 - Primers
4 - Crimp
Hope this helps!

 

[Alex McKr]

BlackRam: All good considerations. It's safe to assume that testing was conducted under controlled laboratory conditions. But...all other conditions can vary. For example :what sort of equipment was used, , ie: Lab mounted test receiver/barrel , or hunting rifle, shotgun, pistol, revolver, etc. System used to measure pressure, and where...ie: PSI vs CUP. At what point on receiver or barrel pressure was tested. Barrel length. Temperature, altitude, etc. Even down to variations from batch to batch of powder.

That's why it's a good habit to check what actual test firearm was used for the load data. Can offer some insight. There can even be minor variations between one brand and even model of firearm, to another.

I suppose the most important, or common sense place to start, is first to understand what are the safe operating limits for your firearm. Then develop loads, from there.

Thanks for sharing

Al