Earlier this year I acquired this Martini sporting rifle. i have been trying to develop a smokeless powder load for the rifle with no luck.

The groove diameter of the rifle is .458. I have been working with .462 500 gr. bullets with groups that would not qualify as patterns let alone groups. Today I fired 8 rounds and only 4 hit the target board. The Target board is 6 ft. wide and 4 ft tall. The 4 that hit the target were in a group 14 inches wide by 30 inches tall. There was indication that the 4 that missed the target board went under and over the board.

I also brought along some .459 diameter 418 gr. bullets cast from WW. These bullets are from a Lyman 457193 mould. I got a 5 3/8 in group.

That red dot is 4 inches low and 4 inches left of my point of aim. But the that's easier to deal with once I get a load for the rifle.

On the way home from the range I got to thinking and decided to check the twist on my rifle when I got home. Turns out it is 1 in 33 inches.

I need a shorter-lighter bullet.

Was there an Express load for the 577/.450 Martini? I see the .450 BP Express loads were from .275 gr to .365gr.