conversion factor?

[Mr. 16 gauge]

If you have a shotgun shell loader, throw a round of powder and weigh it. Be careful whatever you do.

Wouldn't be helpful in this case; modern shotshell loaders use bushings and throw the charges in grains, not drams.....the "drams equivalent" listed on the boxes is a holdover from the transition from black powder to smokeless, much the same as "High brass" shotshells are.