A while back I pulled some info from one of the powder manufacturer's we sites. Looking mostly for pressure ratings. I load only Rem. nitro hulls. Since there was no load data for cheddite primers I was told they are similar to Winchester primers. Since I just purchased two 8# jugs of clay dot that info is what I jotted down.
rem. Nitro hull, claycuster 4100 wad, cheddite primer:
17.5grs. 5400psi, 1200fps
18.5grs., 5760psi, 1250fps
19.0grs., 7020psi, 1310fps
Same load components with a Rem209a primer and Clays Powder
16.9grs., 5800psi, 1200fps
18.2grs., 6700psi, 1250fps
19.6grs., 7600psi, 1300fps
All loads are with 7/8oz of 7&1/2
I also contacted a test facility in Maryland to see exactly what pressures my loads were since I have a Damascus barreled Parker. The gentleman I spoke to said they would do five four shot tests and because it was just me personally and I was not loading to sell the ammo, he would give me a break in the price. Normal price was$700.00 and they would do it for me for $500.00. Needless to say I will just go by the data I received from th web site.
Tom

Dan, to know what the chokes really are you need to measure the bore and the end of the barrel. You could have bores as big as .740 or more. Those bore gauges are only good if the bores are .729, and many modern guns are back bored, the old ones were made larger or have been honed at some time. You have tight chokes, but could be more than you think. For 3/4oz shot loads, most like about 1300fps to get the pattern to open a bit and not get a " hot center". Tom, I believe Precision Reloading will test shells for $5 a shell. Tom Amberst [ SP ?] will also do it for about the same price.