Interesting results

[Slim Chance]

I was finally able to shoot my 1885 Browning Traditional Hunter again. Probably fifteen years since the last time. Caliber is 38-55. I cast a 250 grain plain based bullet of around 250 grains, sized it to .376 and lubed with SPG.
Rounds loaded with 9.5 grains of Trail Boss shot about 6 inches higher than point of aim. The ones loaded with 21.5 grains of AA5744 were spot on. Recoil with the 5744 was noticeably more and published data shows it should be around 300 fps faster than the TB loads. Any idea why the slower loads shot higher?

[Bookworm]

It's called " bore dwell " time. The slower projectile spends more time in the barrel, allowing recoil (muzzle rise) to act on it, raising point of impact.

Faster boolit, less time in barrel, less time for recoil, lower impact.

[Calamity Jake]

^^^^^^What he said!!!!

[Slim Chance]

I understand the principle. However, I have seen the opposite effect more often.

[jcren]

It can depend a lot on hold. For instance with slower loads on my 30-06, if I hold down on the front sling in front of the bench rest, they shoot several inches lower than if I let the rifle lay loose on the rest.