It would help to know the twist as some of them did have a 1-32 twist, but I will hazard to guess it has a 1-48 twist. Who made the rifle.. Investarms, Cabelas, Lyman, Pedersolli?

I think on problem I see is the ball and patch size. Some of the Italian rifles have a little larger bore. I would move a patch size up to .018 and see if that makes a difference. Or go to a .495 ball. When you load the patch and ball.. does it load and slide down the barrel real easy?

If it is loading real easy, you might be getting a gas escape in the patch. With that rifle the least I would run is a .015 patch. The powder sounds about rifle for the charge.

On the ignition.. with the #11 cap. If you are using the factory nipple, replace it with a hot shot nipple. For some reason those Italian factory nipples cause ignition problems. Next... Are you swabbing between shots? If you are, make sure that bore is dry, or you WILL have ignition problems. Also pick the nipple from time to time, make sure that nipple is clean. If you are shooting CCI (standard) caps.. that could be your problem. Go to the CCI Magnum or some Remington #11 caps.

When you first get ready to shoot the rifle, swab the bore of the rifle with pure isopropyl alcohol Then a couple dry patches. Next push a dry patch all the way down the bore to the breech and pop a cap.Pull that patch and check it for a burn mark. If there is not one, push it back down the bore and pop another cap. Check again for a burn mark. Do this UNTIL YOU GET a burn mark.

Many times when we clean and oil our rifles, oil will work in to the bolster. It is necessary to swab all the oil out of the bore, and pop enough caps through the nipple to blow that bolster clear of oil and what ever.

Next, after you pour your powder, turn the rifle to the side, lock facing the ground. Now slap that lock with the flat of your hand. By doing this you know powder out of the breech chamber, into the bolster and under the cap. So when ignition is made, the spark reached powder immediately and you get a good fast ignition.

Also if the rifle is a fast twist, try some conicals. Some of the Great Plains conicals by Hornady, maybe some powerbelts, or Hornady FPB's, even maxiball. The faster twist rifles like the 1-32 like conicals and even sabots.

These are just a few suggestions. I am sure I missed some key points.