9.5 pounds is perfect for a double - or single for that matter. Any lighter than that and it would be less fun to shoot, and shoot, and shoot.

Now, a cast bullet mould, same weight, same loads - straight WW metal should work find, or water dropped to harden - probably not necessary.

for plinking bullets I water drop, then size and lube (usually only lube in ovesize die unless as-cast are too large) within 1/2 hour or so, and 12 hours later, they come to about full hardness & are ready to load and shoot.

For serious work,(hunting), I usually shoot as-cast to obtain some expansion. There is usually no leading in the large bores and excellent accuracy.