Roger,
That is a good start, but not really encouraging for OE. The only thing I can think of is that if OE is close to Swiss in perkiness, it might be damaging the patches. Even with humble Graf's 3f, I have to use fairly heavy denim patches (at least 0.022" maybe as much as 0.025" depending on measurement) or it starts burning "wet" patches with 50 gr. or more in both my .50 and esp. (the "new") .40 GM barrels. Just an observation.
Also, my .50 actually prefers .490 balls to .495 with that patch/powder also. There's no difference in loading, so I don't think it is bore roughness or cutting during loading at muzzle. Still working on it -- bigger should always be better, but in this case not so far!
I need powder soon, so I will see if OE is available to test when I get some. My .50 loves 2F (although I have a light/plinking target load with 3F for it) and my .40 so far seems to like 3F, although I haven't given it much choice yet
.