Powder for steel vs lead in shotgun reload

[sirtunes]

Howdy
Can someone explain in easy to understand language why it requires so much more powder to load 1 oz. of steel vs 1 oz. of lead? How much steel would accept the same amount of 1 oz. lead?

 

[George P]

What loads are you talking about? Where is the data coming from?

 

[tmd16556]

Steel works best at high velocities so you’ll likely notice that in the load data too. High velocity means a slow burning powder to keep pressure from going too high. Those tend to be powders that have more weight per load even with lead. If you compare red dot to blue dot or 700X vs 800X the slower burners tend to be heavier loads.

I’m not a chemist but I assume this is due to more moderating material to slow the burn rate vs pure nitroglycerin or nitrocellulose.

 

[blue32]

My guess would be the identical load of steel would require more pellets and more powder would be required to obtain a satisfactory group.

 

[mokin]

Shotshells are interesting critters. Let's start with your one ounce load. Since steel doesn't weigh as much as lead, a one ounce load of #4 steel shot will contain 192 pellets while the same once ounce of lead will contain 135 pellets. The pellets are the same size so the steel takes up more space in the hull. As tmd16556 pointed out, steel needs more velocity. This is because steel is lighter as looses velocity faster than lead. To achieve the higher velocity, steel uses slower powder and more of it. Just for fun, as I have been loading some shotshells with Titegroup (rated 4 on the burn rate chart) and International (16), the only data for comparable loads using steel shot required about the more powder of Universal (30) to get velocities that began to match what I could get with lead. Basically, you are trying to stuff more into a hull with steel shot than with lead.

Here's an interesting chart that might help demonstrate some of what I've tried to explain.

AVERAGE PELLET COUNT FOR SHOTSHELLS (drundel.com)