Seems like a heck of a lot of powder for a .40. To me the whole idea of small caliber guns was to use a lot less lead and powder. Just my opinion.
As the OP was using Mr. Flintock lube, a very slippery lube, I would not have been surprised to see him using 65gr. 3F. That is what my rifle with a
Goodoien barrel demanded I use to get the same accuracy as 10gr. less powder with a water based lube. With 2F GOEX, I had to use 75gr. GOEX.
These loads produced 2,240fps in my rifle. I was using a bore sized ball and 10 ounce denim. Now, there is a difference in measurement of 10 ounce
denim dependent on the manufacturer. Years ago, the 10 ounce we received from a sewing store here in town, measured .0225" compressed as hard
as I could squeeze the tine together of my calipers, between forefinger and thumb. This newest batch from a different store, measures .021" with the
same calipers. I have 3 sets of calipers and with them I get 3 different measurements, so that is also a variable as to what various cloths measure. I
would suggest that if you are getting some scorching with 10 ounce, then try some 11 ounce denim from Joanne's Fabrics (in the States).