I should add another friend bet the farm on a .40-82 and a 17" twist. He could not get a bullet to 1000 yds most of the time. No exaggeration. it just would not stay stable long enough to make the flight.
On my .40-65 with the same 1:16" twist all the ballistic data I found said that a 400-420 gr. bullet was best for that twist rate. But I tried all sorts of powders, charges, with a Snover and it seemed to begin to destabilize at just over 600 yds. I printed it on paper and although groups were pretty good at 650 yds., the bullets were beginning to keyhole. But the lighter 300 and 350 grain bullets stayed stable at the same distance, and even at 700 yds. were still stable. Both loads were moving closer to 1400 fps to get best accuracy and stability.
Surprisingly my Ballard Pacific in .40-85 Everlasting likes both bullets in 300-350, and the 420 Snover equally well, and shoots them just as accurately. It's an original barrel in minty condition, and has the 1:20 twist rate. Should not shoot the heavier bullets well, but it doesn't seem to know it shouldn't. It's equipped with an unusual tall midrange that falls between the Ballard Long range and the Ballard Midrange. Pretty rare sight.
