Using Starline .455 Webley brass
I poured 3.25g of W231 over a Reed 265g wc; sized to .454.
A Reed 250 RN was also coated with mica to add a little extra diameter and lubrication.
I also used a cast, no lube groove, crosshatched 250g bullet and powder coated to get a little bigger diameter.
I estimate all 3 loads gave under 700fps.
The accuracy was 2.5" to 3.5" @25yds. This was my first handload attempts with the 455 and have not run ladder tests to find the optimal powder weight for each bullet. I expect to get half that group size after testing and chrono.
You should anticipate a problem trying to keep your bullets's diameters after seating. Unless you have a .455 or larger plug/stem on your expander die, you are probably going to swage them down to under .451. Those too small bullets will wobble down the chamber and hit the forcing cone sideways. That will spit shaved lead in your face, lead the barrel, and kill accuracy.
I bought the 45-70 "M" die expander plug from Lyman that has .456 plug. After running brass through the .456 expander it will "spring back" from .001" to .002" and leave your brass with a .454 nest for your .454 bullet. Lube or wax your brass cases or they will stick like glue on that expander stem.
These cartridges and bullets reminded me of SNL and the coneheads. They looked like fat, squat, rounds with a big upside down snowcone head on it. Cute as all getout.
Fun caliber to play with.
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My pistola has been modified to also shoot 45 Colts. They counter sunk the chambers to allow the bigger and thicker case rim of the 45 Colt brass to fit. This is the best approach I've seen when modifying 455 to shoot both .455 Webley and the 45Colt.
I kept all my 45Colt loads under 800fps as I was nervous about the old shooter handling higher pressures.
Let me know if you want that data as well.