I have a hexagonal very heavy barreled percussion rifle with a false muzzle. I see these sometimes called target or sniper rifles. The barrel is stamped "gain twist" and the locks are Golcher. The barrel appears reused from another gun. Also, stamped on the gun is Roth, who was a gunmaker in I think Pennsylvania, and later a principle of Wilkes Barre Gun Co., along with maybe Parry, Tonks , and others. I really have nothing to add except the stamped "gain twist". The gun has a set trigger.

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