Does anyone here know if there has been a significant change in the burn rate of IMR 4064 in the past few years?
I ask because I am noticing a big difference in 7mm-08 loads in my two Sierra manuals.
Specifically:
4th edition (50th anniversary)
7mm-08
168 SMK
Max load of IMR 4064 is 42.0 grains
5th edition
7mm-08
168 SMK
Max load of IMR 4064 is 39.2 grains
That is a pretty big drop in the max load.
So what is going on here?
Did the powder change that much?
Different testing methodology?
Or is the 39.2 grain max load a "lawyer" load?
I ask because I am noticing a big difference in 7mm-08 loads in my two Sierra manuals.
Specifically:
4th edition (50th anniversary)
7mm-08
168 SMK
Max load of IMR 4064 is 42.0 grains
5th edition
7mm-08
168 SMK
Max load of IMR 4064 is 39.2 grains
That is a pretty big drop in the max load.
So what is going on here?
Did the powder change that much?
Different testing methodology?
Or is the 39.2 grain max load a "lawyer" load?
