Need help, I'm confused with some info i have. My old horndy manual list's 300 win mag 71 - 79 grains of IMR 4350 for a 150 grain bullet. Top velosity was 3400 fps. I had started on a new rifle and load. Shot some single rounds of the low charges and started loading 3 each starting at 75.5 grains. I didn't show any pressure at 75 grains so i moved to 75.5. Hadn't set up the chronmagraph until then. That set of 3 averaged 3400 @ .043 inches 100 yds. I had 3 more loads at 76.5, 77.5, 78.5 but was afraid to shoot them. It didn't show hardly any pressure up to 75.5 but just a bit of shin on the base. No sticky bolt or hard to open or flat primers. When I got home and got to checking I couldn't find any where that list above 74 grains for that load. What's going on? I've loaded from this manual for a lot of years and never had a problem.
I just looked at the Hodgdon web site and they give loads for two 150 grain bullets using IMR-4350, and I found it to be interesting. With Barnes 150 TTSX the max load is 75.0 grains of IMR-4350 for 3347 ft/sec.. With another 150 grain bullet the max load is listed as 74.0 for a velocity of 3254, so I think you are at or above the max load for a 150 grain bullet.
I have a Hodgdon manual that is close to 20 years old, the data listed for the 7mm Rem Mag, H1000 and 175 grains Hornady bullet shows the starting load above the max load that Hodgdon now lists for this combination. Why?
Is the new data more accurate? Did the burn rate for H1000 change in the last 15 years?
What does this prove? I think it proves that we must look at more that one source for loading information. Thing do change.