ive never had this problem with my .50 triditions deer hunter and im using a .490 round ball and a .015 denim patch lubed with crisco(i keep it in a pellet tin in the possibles bag) of corse the 1 in 48 twist calls for smaller charges then a round ball twist
The 48" twist IS a RB twist and a good one.
Its all that is found in original Hawken rifles for example.
The myth that its not comes from the TC rifles with shallow grooves.
A barrel rifled 1:48 with grooves .008 or deeper with grooves wider than the lands will shoot all the powder needed, 100 gr plus in a 50 caliber.
Dan