I bought two custom rifles based on the Remington Model 30S Express, one in 358 Norma and one in 300 H&H Improved. I bought a set of dies from BIGMAC to start loading up cartridges for the 300 H&H imp. In my reading I found that 300 Weatherby would fit the chamber (I tried one I had on hand and it did chamber). Midway had a good price on Norma 300 Weatherby cases and I obtained 50 from them. I ran the cases through the improved die set and loaded up ten rounds. They shot fine but my question is on loading data. I have a large collection of loading manuals and researched on the internet loading data but couldn't find any. The Ackley manual says just use the Weatherby data but my research shows the difference in the freebore makes that problematic. Using the Nosler number 8 manual it shows a load of 67.0 grains of IMR 4350 as max for the 300 H&H with a Nosler 165 grain solid base bullet with an OAL of 3.600. It shows 76.0/74.0/72.0 grains for the 300 Weatherby with an OAL of 3.560. I loaded with the 72.0 grain load to an OAL of 3.600. My question is does anyone have loading data for the 300 H&H Improved for different bullet weights? With the increased case capacity am I on the correct track for load data?