Hello all. Just joined the forum and this is my first information seeking post. I’m looking to build a 6mm ARC upper to go on my high quality 5.56 multi-cal lower. I spec’ed out and assembled all the parts for my 5.56 build about 15 years ago. So I’m not completely green. I’m looking to build the 6mm upper to be a strict bench rifle and I want to accurately shoot out to 1000 meters and beyond. I know I’ll need new magazines and I’ll have to change out the BCG, or at least the bolt head. There might be some other mods to my lower. But this post is specifically asking about the barrel and gas system. All over the internet, there are so many differing opinions about barrel length, twist rate, rifling and gas system length. I decided to go the round creator and I contacted Hornady. The tech guy said for my application I should get a 24” barrel with a 1:7 twist and a carbine length gas system with an adjustable gas block. I forgot to ask about 4 or 5R rifling. The recommended carbine length gas system seemed a bit short. So here I am asking you folks what you recommend based on your first-hand experience. Please understand I’m not looking for any advice or recommendations on barrel manufacturers or manufacturers of any part for that matter. This is strictly recon on barrel and gas system specs. Once I have gathered enough info and decided on what to get, I will work on who to get parts from. I pre-emptively thank anyone who contributes information to my build!