...........edwin41, one problem I see, and it's probably your MAJOR problem is that the nose of your slug is engraving in the leade. For a bore rider, a small bit of marking by the lands is fine, and desirable. However it is very important that the leading edge of the paper patch isn't getting rucked up when the slug hits the lands.
This is a 420gr pure lead slug for a .43 Spanish. The leading edge of the patch is just over the turn of the ogive. The slug is swaged, hence has no lube groove to accept the leading edge of the paper, so it's patched over the ogive.
The above 577-450's are loaded with 405gr soft cast Lee slugs. The leading edge of the patch is OVER the top drive band. The nose is short and does not touch the lands. Helpfull also is the fact that the chamber and leade are designed for PP'd ammo.
LEFT: This is a 38-55 and as you can see, the lands engrave the slug AND impresses on the patch when chambered. Since the lands immediately engrave upon the paper, the leading edge isn't damaged. On the right is a closeup of another slug (a lube grooved design) patched for use in the afore mentioned .43 Spanish. As you can see, the leading edge of the patch is tucked into a lube groove. The leading edge cannot become damaged.
The above are 530gr grain soft lead HP cup based swaged slugs for use in a long range muzzle loading rifle. Since the entire boolit is in the barrel sitting on the powder charge, there is no need for any special care required for the leading edge of the patch as it's already IN the barrel
A good 30 cal slug for sizing down and then paper patching is the Lyman 311284. At 210grs it might be too heavy for your purposes, but what makes it a good design for paper patching (which I've used it for before) is that it has one of the old fashioned 'So called' dirt scraper groove in front of the first drive band. Convenient place to tuck in the leading edge of the patch.
..................Buckshot