Estates are Federal, which means straight-walled hulls
Clays is Hodgdon.
So, going to the Hodgdon website, we find:
Lead Shot 12 1 1/8 oz. Clays Ched. 209 WAA12 16.3 7,700 PSI 1090
Lead Shot 12 1 1/8 oz. Clays Ched. 209 WAA12 17.3 8,500 PSI 1145
Lead Shot 12 1 1/8 oz. Clays Ched. 209 WAA12 18.5 10,000 PSI 1200
Lead Shot 12 1 1/8 oz. Clays Ched. 209 WAA12 20.5 11,500 PSI 1255
That's using the data for Cheddite hulls
Lead Shot 12 1 1/8 oz. Clays Win. 209 WAA12 16.5 7,300 PSI 1090
Lead Shot 12 1 1/8 oz. Clays Win. 209 WAA12 17.3 8,300 PSI 1145
Lead Shot 12 1 1/8 oz. Clays Win. 209 WAA12 18.6 9,700 PSI 1200
Lead Shot 12 1 1/8 oz. Clays Win. 209 WAA12 19.9 11,000 PSI 1255
That's using Federal Gold Medal hulls
You can see the infamous 17.3 load happens in both, and that 18.5 and 18.6 occur as well. Those are decent mid-range loads with low pressure and would be decent loads for 1-1/8.
After a while, you will realize that 1oz, and even 7/8 oz will break most trap and skeet targets while saving you money on lead and your shoulder from recoil
Good luck