This will be a "Well, duh..." for most of you.
I tend to shoot light loads in my .50 to baby my shoulder, which gives me some trouble. I was shooting 75 grains of 2F and spraying round balls across the countryside. Just the other day I decided that with a new piece of foam in my jury-rigged pad I could try 80 grains.
Suddenly I was a better shooter. My shots coalesced into a 1 1/2" ragged hole at 25 yards offhand. Still a few flyers - I'm not Daniel Boone - but the rifle is now shooting where I point it. I know as soon as I pull the trigger that I've twitched it to the left, or wherever, and that's where it went.
Funny how those threshold effects work.