Unknown ingot material

It’s been a long time but it’s good to be back playing with lead again.
I’ve just acquired 30 1lb ingots cast from Lee molds.
I just cast some 452 diameter boolits from a Lee mold grain weight 255.
However, my boolits are coming out at 265 grains. Doing the old scratch test, the castings appear hard. Any suggestions on what I can do to get them a bit lighter?

Add more tin. 5% should work nicely.

Shoot them. Why worry? No one expects Lee molds to mold bullets exactly to the weight they say they will be. The higher the pure lead in your alloys composition, the higher the weight your mold will cast bullets. AND the smaller they will cast.

Shoot as is and see if you are satisfied with results
Mike