Morning Gents..First post..I ordered a CZ527 carbine in .223 to convert to a .257/223 project ...I'm wanting to have a gunsmith just rebore the barrel to 257 Dia. & leave the chamber as is..I want this carbine to shoot the Lyman 65 Gr gas checked cast bullet & up to say 90 Gr Jacketed stuff...The old 25-20 used a 1-14 twist..My old 257 Roberts shot this bullet pretty well using a one in ten twist rate..My plan is to split the Diff on the conversion..1 in 12...not sure of the number pattern lands grooves..Any thoughts you would like to add to this project that can help me avoid pitfalls in the design would be appreciated...Mike