I writing as you guys are posting but....every shotgun shelland thebox is usuallylabeled about how much weight of shotit contains.
For instance, a 20 gauge shell could be labeled as having 7/8's of an ounce of shot if it's a low brass general purpose load, or more if it's a high brass hunting load.
A 12 gauge shell could also have a 7/8's ounce or 1 ounceload if it's a low brass target load, ormore if it's a high brass, long rangetrap load or hunting load.
A 12 gauge load willusually have moreshot, but how much moredepends on the weight of the specific shell.
Generallya 12gaugewill have 1/8 to 3/8's of an ounce more shot than a 20 gauge, but again, not always.
According to one Wikipediachart that I found, there are 120 pellets of #7 shot in 10 grams of lead. That equals about 340 pellets of #7 shot per ounce, whetherthe shell isa 20 gaugeor12 gauge. A 7/8 oz. load wouldhave about 298 pellets.
A 1 1/8 oz. load wouldhave about382 pellets of #7 shot, and 1 1/4 oz. load wouldhave about425 pellets of #7 shot.
So onepossiblehypotheticalexample might be that a 7/8 oz. 20 gauge load could have 298 pelletsof #7 shot versesa 340pellet 1 oz. 12 gauge load. But that's just onepossible example of a comparative load.
http://en.wikipedia.org/wiki/Shotgun