Hello all. I have been studying the 45-70 cartridge and firearm for long range for about 5 years. I have built my first rifle in .30 WCF from scratch (Check out my thread on special projects) that I took around 3 years of studying to gather information about how to do it, now I want to build a long range 45-70. The question is about rate of twist, number of grooves and barrel length. All of my research has led me to a 28"- 30" barrel with a 3 groove 1:18" twist. What would be your suggestion? I plan on this being a 45-70/80-500 Lead boolit load in a 2.4" case. Thanks in advance for any input.