Caliber of/powder weight behind a shotgun slug?

[Mike-SoCal]

I'd like to use the Taylor Knockout Scale (mass*velocity*caliber/7000)) and the recoil calculator as these relate to a 10ga and a 12ga shotgun slug. I have the bullet weight, 1.3/4oz (766gr.) & 1.3/8oz (600gr.) and the speeds, 1280 f/s & 1502 f/s at the muzzle. What I need are the equivalent calibers and a way to determine the powder weight in grains when none are listed on the manufacture's website. Any help on the last two items would be greatly appreciated. Thanks.

 

[Dave McC]

12 gauge is .729" nominally, 10 gauge around .76, IIRC.

There's no standard weight for powder.

In older times, 12, 10 and 8 bores were shot with black powder charges oft determined by volume, thus the dram method.

Grain weight of the powder can be determined by dissecting a shell.

HTH....

 

[Poodleshooter]

Most 12ga slugs use a weight of powder amounting to somewhere between 30-45grs. Usually this is a medium-slow magnum pistol powder such as HS6 or HS7.
No clue for 10ga.