Hi Lexington1,
Thank you for posting these pictures. It is a wonderful gun and the design typifies English rifles from the 1730s-1750s, muzzleloading and breechloading. The screw plug breech goes way back into the 17th century. Sometimes it was on top, sometime on the bottom. These were "deer park" rifles and slow loading was not an issue. I know many are focused on the breech loading mechanism but the gun has lessons for any English rifles of the period. First and foremost, the breech and wrist are massive! You can see that this is a very robust gun through the lock and wrist sections. The famous Turvey rifle in RCA 1 is the same. The published photos just don't reveal how big the gun is. It was an eye opener for me when I saw the RCA 1 Turvey at the exhibition at Rockford Plantation. Think Edward Marshall rifle size rather than English fowler size. John George in his great book "English Guns and Rifles" described how English rifle makers during the mid to late 18th century subscribed to the idea of many grooves and fast twist even in big bores. John George discussed how that notion created very accurate rifles shooting patched round balls but only with relatively light loads for the calibers. Otherwise, the patched bullet would strip the fast twist rifling. He wrote how those rifles worked well out to 100 yards but failed miserably at longer ranges. That was the source of the great debate about rifling that propelled Ezekiel Baker to the forefront. He knew that a slow twist would better suit patched round ball accuracy under heavy loads for distance and the number of grooves did not matter that much. Keep in mind that before Benjamin Robins published his paper on ballistics in 1742, no gunmakers anywhere understood the physics controlling rifling and accurate shooting. Finally, it is interesting to note correspondence by Phillip Lee (ancestor to Harry Lee and Robert E. Lee) in the 1740s extolled Turvey rifles proclaiming they were much better than the local products.
dave