A common misconception about back action locks. They can easily date to the 1830's, as this rifle pretty much verifies. Philadelphia is one place where pistol-grip stocks were not uncommon. I have a rifle with pistol-grip stock, made by Joseph Butler in Chicago, who worked briefly in Philadelphia , after his arrival from England. Butler was the son-in-law of James Golcher, the noted Philadelphia gunmaker. Golcher was also from England.