I have data for two different 175 grain Lyman bullets using 231, both cast using the # 2 alloy. Results are from a universal receiver with a 4 inch barrel, 1-16 twist.
First is #401043, by the illustration a round nose flat point bullet. It lists the starting point at 4.3 grains with 863 fps and the max at 5.8 grains with 977 fps. Pressure at max is listed at 22,500 CUP. Overall length for this bullet is given at 1.125 inch.
Second is #401638, by illustration a conical flat point bullet that appears to be a bit shorter in length than the above RNFP. BTW, it really bugs me when these data manuals don't list the overall length of the bullet. Starting point is again 4.3 grains with velocity of 796 fps. Max load is 5.8 grains with a velocity of 970 fps. Overall length listed with this bullet is 1.100 inch.
Take note of the difference in the overall length. I expect that the reason for this is because the second bullet is 0.025 inch or more shorter than the first. Which is why I find it frustrating and lacking when load data tables don't include the length of the bullet. If we knew the length of these particular bullets you would be able to measure your bullet and come up with a far more accurate starting length by maintaining a constant case volume behind the bullet. Without that critical bit of information I can only recommend starting in the 1.135 inch range and test for function, accuracy, and feel.
