I have known these to be used in the past but i am not sure if you want the 3/4 or 7/8's disks for 12ga shot shells???? anyone ever tried this and how well did they work for you. I am just going to start roll crimping buckshot. thank you!

3/4" for 12ga

thank you for the response

I'm interested in how they would work pushing a hard plastiic .750" disc down a .729 bore and even smaller choke and hoping for good patterns.

BPI makes a clear plastic frangible over shot disc that work quite well.

https://www.ballisticproducts.com/Clear-Overshot-Discs/products/112/

They break apart before they reach the constriction. Shouldn't affect the pattern any. They make a clean looking shell.