Paul Mathews writes in THE Paper Jacket of using a bore dia. (land-land) bullet before patching using black powder.  He states this is for target use..needing to clean after each shot as opposed to using a smaller unpatched bullet for hunting.  Has anyone used a bullet this large?  I would think a thin patch would be needed?

I have shot a .45 X 2 7/8" Sharps using the Postell bullet that cast up around .457 Diameter. I Pan lubed them with
Pope lube and then ran them thru a .452 Lube die. We then shot it with Duplex Black powder load of 10 grs 4759 and 100 Grs of Elephant Fg  at 1000 yds. It shot very well indeed. The Postell was 30/1 and 535 Grs. The Rifle weighed about 11 Lbs. Kicked like a Mule. So this was a grease grove bullet with no Paper patch. We ended up with a group at 1000 that measured right around 10" so it will work. HTH Regards, FITZ.

Here is what I have:  Years ago, I had Tom Ballard make an adjustable .399 P.P. mould.  At the time, I had sworn off black, and this was to be used with smokeless in a .40-70 2 1/2".  Slugs drop at .400 with 20-1 alloy.  Now I have gotten back to black..thanks to the Swiss powders..but wondering if mould dia. is too large?  I plan on trying 30-1.  I did try this..took a patched bullet that measured .408" dia., lightly lubed with soft beeswax based lube & ran it thru a Corbin reloading-press type bullet reducing die.  Bullet now had a very hard feel to paper & very shiny.  Bullet dia. over patch mikes .4025".  I unwrapped paper & slug mikes .394"  I wonder if this process will work..could try thinner paper to leave slug larger dia. & dia. over patch smaller?  What do you guys think?

The use of bore-dia bullets patched to groove is pretty normal - in fact, I do it all the time with BP in several rifles.  No tearing of the patch, no  issues with the throat - nothing.
Of course, your chamber should be able to accept the bullet, but if it will accept a groove-dia. GG bullet, then it will also shoot the groove-dia. PP bullet.

Contrary to popular opinion, PP patched to groove dia. was being used quite a lot, even if mostly in the old world.  In actual fact, the last cartridges produced by Kynoch with PP bullets all had bore-dia. bullets patched to groove dia.
Finding paper of the correct thickness isn't all that difficult, and you can always size after patching if it's a bit off.  Actually, you can even patch to somewhere in between without any problems.  .458 in a .462 bore will work quite well indeed.
No need to swage down or perform weird things, just load and shoot.  And wipe between shots, of course...