Is brass for the 243 AI readily available? Or would i need to make some alterations to regular 243 brass? I am considering building a 243AI and was curious about the brass situation. Will the 243 AI shoot light bullets for varmints like the standard 243? I want this gun to be a varmint/deer combo gun capable of handling loads as light as 60grn and heavy as 105 grn. What is the standard twist rate of a 243? I know in the original 6mm(244) it was 1in12 and I was thinking 1in10 or so. Am i on the right track here?