Old load data or new load data?

[Grandpa Shooter]

I went on the manuacturer's sites for updated load data for what I load. Looked at the new data and then got out my old loading books (they were current for the primers and powder I own) and discovered a significant difference in charge weights of powder for the same bullet For example in my old Accurate book for 125(L) RN No2 min 4.1 max 4.5
New website data 125(L) RN No2 min 4.2 max 5.0

Can any of you explain the change? Is it rated higher for newer guns? Has testing revealed hotter charges are safer than previously thought. Is the newer powder formulated differently than 10 years ago.

I figure since my supplies, books, and firearms are the same vintage I will keep using the old data unless you guys know something I don't.

Fire away when ready!

 

[steveno]

probably due to slight variations in powder lots. as long as you start low and go up it isn't a problem. never start at the max load

 

[Clark]

I assume you are talking about 9mm Luger.

According to Quickload, one would need 5.1 gr of AA#2 to reach the SAAMI registered max average pressure of 35,000 psi.

Risk averse lawyered up corporations sell 9mm +P+ factory ammo, which in these terms, would be more like 5.4 gr.
[9mm has safety margin]