Todd- in my opinion, judging by the brown, heavy brown and brown streaks to the outside of the patch, you are not getting a good seal.
The cuts you see are likely from a machine-cup muzzle crown. The lands are cutting the patch when loading.
All of these observations mean
you are very close to a sealing load for the powder charge you are using. More powder will blow more patches, simple as that. A tighter seal
by using a thicker patch might not be possible until you smooth the crown on the muzzle. I am glad to see you using FFG powder. FFFG will create
even more pressure even if loaded down to 75 or 80gr., which is likely the same velocity as you are getting with 90gr. 2F. 2F will give less pressure
at ANY given velocity. I find better accuracy even in my .50, using 2F rather than 3F.
So- conclusions: re-crown the muzzle. It is easy, then there will be no more cutting of the patches on the lands when loading. The combination is close
but a slightly thicker (10oz. denim) patch will help, or using a .535" ball and the same .018" patch. That should do it.
Again, you are close. The dirty in the bottom of the barrel, is due to blow-by at the instant of ignition, usually. That your patches are wet, yet still scorched
so badly, even in the middle, shows the olive oil sucks as a patch lube - in your gun. Track's Mink Oil, Neetsfoot Oil, your own spit, WWWF or windshield washer fluid all
do a better job.
Note: water based (includes spit) are bad for hunting purposes - they will promote a rusted ring where the ball sits.
A little emery, or wet/dry (I like 320 grit) in the muzzle, pushed by the end of your thumb, rotate your wrist, turn the barrel now and then- every 15 seconds or so,
and in 1 minute you are done. Shove a bit of patch material into the muzzle to catch stone and metal grindings, then pull it out when done.
Machine cut crown
emery'd crown
method
