Re: 12 Ga shells
1 dram is 1/16 of a ounce. Black powder shotshells used to be loaded with so-many drams of powder.
People that shot a lot of shotshells knew how powerful a shell loaded with 2 3/4 drams of powder, or 3 1/8 drams of powder were.
When smokeless powder came along, you did not use anywhere near as much of the smokeless as you did the black, to get the same ballistics. The manufacturers started marking the boxes with "dram equivalent", so the buyers would know what the performance was.
One dram of powder was 27.3 grains, so a standard load of 3 drams is 82 grains. The actual charge of smokeless might be 25 grains. Putting that on the box would just confuse the buyer. So they would mark the box 3.0 Dram Equivalent, or 3 Dr Eq. This let the buyer know that it was equivalent to having a shell loaded with 3 drams, or 82 grains, of black powder.
Nowadays nobody knows what that means. When I started with shotguns, in the 70s, all it meant to me was 3 1/4 dr eq was a more powerful load than 3 dr eq. The makers still put it on the boxes, out of habit.
Some makers, though, have started putting velocities on the box.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.