I bought a pound to test, but found what appears to be an error on the Hodgdon website load data. Loads listed for .243 Win seem to be mixed up. Specifically, max loads for some of the heavier bullets are shown as:

90 gr Speer Soft Point, 40.5 gr 4451
95 gr Nosler Partition, 41.8 gr 4451
100 gr Speer Soft Point Boat Tail,42.7 gr 4451

...all at essentially the same pressure. It doesn't make sense to me that you can load heavier bullets with more powder and maintain the same pressure. Starting loads listed follow a similar pattern. I recognize that the bullets listed have different characteristics, but that can't explain what's shown. I called Mike at Hodgdon, who checked back to their actual test data records and he said these numbers are correct. I'm stumped. Does anyone have any experience with this powder? Can anyone offer an explanation?

The bullets are different designs with different bearing surfaces. Bullet weight alone doesn't entirely determine pressure characteristics. That said, you might want start low and work up with a chronograph.

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bearing surface and bullet length both can come into play. Heavier more rounded bullets have more weight outside the case not taking up powder room

Thanks for the input. I recognize that bearing surface, jacket hardness, thickness, bullet jump, seating depth, pressure curve and lots of other things can have some influence. But here's an interesting fact. The Speer Manual No 13 includes loads for two of the tested bullets. For every powder listed, the charge weight for the 100 gr. BTSP is significantly lower than for the 90 gr. SP. No powder shows a higher charge for the heavier bullet. I'm still skeptical. I'll just start low, measuring velocity and watching for signs of pressure.

Wise decision

I've got 4lbs coming to try in my creedmoor. Reports from other shooters are very promising.

Yes, sometimes the data is a little misleading. If you apply a little logic to similar powders in the same burn rate, it can help you out. The 4451 is very similar to IMR 4350 (and H4350). So, you can piggy back that data and apply it to 4451. I do this often when there isn't any load data to go from, especially when you have a new powder out that doesn't have a lot of forum data or from other shooters. This powder will work well for you, though.

Chad, I'm testing the 4451 as a replacement for IMR 4350, which I have used for over 30 years. I've never seen a charge weight for IMR 4350 that went up with heavier bullets, in any caliber. I'll just start slow.