Re: green mountain barrels
Green mountain barrels are better than most production barrels. There are better barrels than Green Mountain, but the cost is multiplied.
It really depends on your purpose. If you want a good hunting gun, green mountain is good, or if you want to set a new world 100yd bench gun record, you'll need a better barrel. Just as there is fast twist for conicals and slow twist for round balls, there are different configurations of rifling for different purposes. Round bottom rifling seems to make it easier to keep the bore clean for shooting several consecutive shots,
Most green mountain barrels for round balls are capable of three inch groups at 100 yds. But to get to that point, there are so many other factors, barrel crown, loading consistency, ignition consistency and speed, sight picture, and shooter.