I was told it would keep the rifling sharp at the crown. Kinda like accuracy suffers as the crown wears. I literally wore out the crown on my 1979 T/C Hawkin even though only brass ever touched. I'm guessing 20,000 rounds thru it in 20+ years, tho. Toward the end it wouldn't even shoot maxi-balls very well. Again, just my honest opinion...
And the flitz polishes it up quick!