as bushing you can get
steel bushing that made in high carbon steel, 1% or close with chromium alloy to get high hardeness ) hardness is in 60 to 62 hrc
stainless steel bushing that a tool steel alloy with more carbon, chromium, more to make stainless effect ) and molydeum and some time vandium hardness is close to the same as steel bushing but the stainless
carbide, they are made in full carbide hardness is the carbide hardness and that closely self lubricating so no need of lub
coated bushing you can get bushing with TI nitrated, yellow ) th emost commun, carbo nirated titanium, purple ) that more hard and high performance that the yellow coating and carbo aluminium oxyde - look as shimmy white coating ) that the harder coating but that use more for light alloy cutting
trace on neck came from galling of brass inside of the bushing, the cooper remover way is a way to solve the problem
I use ball bearing small cup with moly powder, 1/16 ball size ) to lubricate my neck before to size and get any problem with steel bushing, this items is available from Neco as original product or can be located from Sinclair too or can be made esay with ocal supllier, ball bearing from supllier for tumbling equipement and moly powder from Bel ray or any other company )
good shooting and enjoy belgium wafles for Eddy
DAN TEC