SJA,
The 21/2 inch Explora shot the 730gr LT capped bullet at 1250fps. the cordite load was probably around 33grs. Some guns shoot standard paradox cast bullets well others don't. G. Wrights book has several loads that might do well in your gun. You can use shotshell cases, I like federal paper cases. How long have you had your Explora, is it a droplock? What are the barrel diameters and how does the rifling in the chock look?
PM