Did you mean 280-290gr?That is a good question. Cast or jacketed?
With a bullet of .43-.432" in a 1/38 twist, the ideal weight is between 180-190 grains based on the Greenhill Formula. I have had some success with bullets in that weight, but I am of the opinion that the ideal bearing surface of jacketed bullets is about the same as the bearing surface of the bullets made for it. If you look at the 240gr Rem bullet and the Hornady 265 fp, I am willing to bet that you would be in the ball park.
Starrbow might be able to offer some insight if'n he makes it around to see this thread.
Ranch Dog talked to me about this issue and as I remember, he said that the RD 432-240/250 is about as short as he would want to go with a cast bullet. Then again, he was looking at more than bearing surface, but taking into account the for/aft weight distribution for in flight stability. There is part of the equation that includes nose length, type and weight into that account as well.
Is that a fuzzy enough of an answer for you? How's this? if your between .30" and .55" with a properly sized bullet, you should be good to go.