Question about reloading data

[Devo64]

Hello, I have 2 questions for everyone, I have a 28 nosler and am trying to work up some loads. I'm new to reloading,
why does it say in the sierra manual that for a 168 hpbt match bullet it takes a powder charge of retumbo 71.4-76.4.
and in the nosler manual it says 79.0-83.0? Also if you under load will it cause more pressure?

 

[338 dude]

Hello, I have 2 questions for everyone, I have a 28 nosler and am trying to work up some loads. I'm new to reloading,
why does it say in the sierra manual that for a 168 hpbt match bullet it takes a powder charge of retumbo 71.4-76.4.
and in the nosler manual it says 79.0-83.0? Also if you under load will it cause more pressure?

Each company is testing with their bullet although they are the same weight they are two different bullets also some manuals say the length and twist of the barrel they were tested with and that may vary between the two companies as well

 

[26Reload]

As Jr. said.....each company test firing 'their own bullets'...
those bullets may be same weight...but different lenghts...
and in those lenghts is the key to pressure....
the bullet with more bearing surface could cause more pressure....i say could..because some guys on here are coating their bullets to help them slip thru the barrel faster....
Definitely follow the book on you specific bullet...