So, I read your post and didn’t see you planned shooting range desired. I saw the bit about energy, but not your purpose for this weapon. I will also ask your experience in shooting as well, for my own info to assist you. Nothing wrong with a 12.5” out to 400. 16” to 800. The thing I will correct you on is your statement on accuracy. The shorter barrels are no less accurate but suffer from velocity loss resulting in drop, not a loss in accuracy. Wind will affect a projectile more with less weight and velocity.