Hodgdon 777 FF in 45-70 Rounds

So this was an experiment I was very excited about. I loaded 2 flavors of rounds, unknown 405gr greased flat nose and Missouri Bullet Co #2 Buffalo 300gr rnfp with the Hi-Tec coating. Now I loaded these rounds back in February '23 just before my eye problems started. Now a year and a quarter later I'm starting to return to normal so I took the trapdoor to the range to try them out. While still having a slight degree of difficulty with the Buffington peep I kept my form consistent which worked well with the other rifles on hand. I was very less than impressed by the accuracy of these rounds. They were all over the target, more of a pattern than grouping.

The load was 85% of the normal BP 70gr load as black powder substitutes are more powerful than BP. That's what Hodgdon lists as safe loadings. So that works out to 59.5gr of the 777 however not having a measure with half grain increments I rounded up to 60grs. I used pre-cut .462 diameter vegetable fibre wads between the bullets and the powder.

Has anyone else loaded 45-70 rounds with Hodgdon 777 FF and had disappointing results? As a side note my similar rounds with IMR 3031 or Hodgdon 4350 are really very accurate in this rifle.