I would get a BP Powder measure:
https://www.sportsmansguide.com/product/index/cva-range-model-powder-measure?a=417627
Fill it will 100grains of Pyrodex, dump that in the tube, and see where it lines up. If it doesn't match the markings on the tube, I'd make my own markings.
https://www.sportsmansguide.com/product/index/cva-range-model-powder-measure?a=417627
Fill it will 100grains of Pyrodex, dump that in the tube, and see where it lines up. If it doesn't match the markings on the tube, I'd make my own markings.