I had some Graf's 3F that shot same trajectory as Goex 3F, if not a little better, then I have some more recent that seems to lose velocity w/ref. to Goex, esp. in heat and/or humidity. It is cleaner than Goex in my experience in terms of amount of fouling, but the fouling (at least of the current batch) reacts more to hot, humid weather and makes a mess quicker.
My .50 seems to like 2F better after a couple thousand shots, and it takes a good chaw out of the can every shot, so I've been tempted to try the Graf's 2F on sale, but I'm not sure it is good economy if I have to bump charge up.
Now, I know I am at risk of sounding silly, but it is it possible for powder to react that noticeably to weather? Is the Graf's maybe a good deal for spring and fall shooting where conditions are more average or is it a change in lots that is causing the problem? I know the mad monk's experiments showed Graf's and Goex were neck and neck in terms of velocity (thus trajectory), and some of my experience backs that up, but some contradicts it.