psteinmayer wrote on Mar 8^th, 2013 at 2:55am:

. . . IMR 4064 is great with the 165 and even 180 grain bullets, but burns too fast for a heavier bullet like the 220 grain.  The powder would be spent before the bullet is 3/4 down the barrel, which means that 1/4 of the barrel length, the bullet is slowing before it reaches the muzzle.  Likewise, a slower burning powder like 4350 with a lighter bullet, the powder is still burning when the bullet leaves the barrel, which results in poor accuracy and performance.

This assertion sounds logical but may not be accurate. Graph below shows predicted burn curve of two 220 gr. loads giving virtually identical velocity and pressure. If the modeling is accurate, 4064 is some 99% burnt in the 30" barrel, while 4350 (with its larger granule size) has left about 8% unburned.
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Modeling software like QuickLoad allows us to hold some of our logical assumptions up to mathematical scrutiny. It's not a perfect tool, but often better than accepting assertions with even less support.