I was sighting in a new peep on my slow twist plains rifle. After I was done with making sure a PRB round ball hunting load was sighted in, I decided on a whim to try a few Lyman 54 plains bullets. I only did a couple of loads, but when I got up to 80 grains of 1.5F OE and an over powder wad, the group was starting to approach the round ball load. I was running out of time and didn't pursue it further, but it seemed like a little more load development might get me close to the tight round ball groups this rifle throws. The bullets cast at 430 grains and it seems like it shouldn't work for a 1 in 60-something twist. Why did it work?