For me, 2F has shown better accuracy from .50 cal. up. Lyman showed many years ago when using pressure equipment,
that 2F also produced lower pressures for duplicate velocities, than 3F produced. Their test gun had a .54 bl. For me and
all of us here in Northern B.C., we don't have fouling problems (with any powder we use) as there is zero fouling buildup, shot
to shot.
Depending on how you load your rifle, maybe there is a buildup of powder and maybe 2F would foul more for you
because of that? Hard to say. There can be a major difficulty making blanket statements as oft times, they do not
effect everyone the same & may in fact, be polar opposites.
The odd guy up here uses 3F in larger than squirrel rifle calibres, but most use 2F for .50's and above - and no one has to
wipe their bores while shooting the trail - ever, thus proving there is no fouling buildup (for us) with either powder, even for well
over 50 or 60 shots fired. To illustrate that statement, Taylor once grabbed the wrong horn and ended up using 1F in his .40 for a trail.
After he found he had to add a little more powder and higher front sight, he commenced to hitting all the targets, as is usual
for him. So - no more fouling, even with 1F, and no accuracy problems either. That was due to him using a .395" ball and .022
Denim patch, thus, he experienced easy loading, all day as normal.