BCRider
Member
After looking over my own open top 1851 I'd have to agree with some of the stuff in Nicodemus' quoted material but some of it is just wrong.
The issue with how the slot in the arbor is "tuned" on my own gun is one that bothers me as well. The metal has been peened to close the gap and then the wedge has be tapped into place to peen these upset areas back to size for a "perfect" fit. However now all the pressure from shooting is being supported by two small contact patches. A far better way would be for the barrel to be fit to the gun and then the front and back of this slot mated using a broaching action or even done by hand using a proper metal file and a jig to ensure the edges are shaped and sized exactly for a perfect mating. Then from there the wedge could be fit to the exact taper before being trimmed for the proper exposure out each end and finished off. With such a method the pressures would be supported by a much larger area of metal.
The other area that made me shake my head was again a tolerances and manufacturing short cut issue. The arbor threading into the frame is a little loose. For the sort of use we are putting this thread to the fit should be a slight interference fit so that some force is needed to torque the arbor home in the frame. Not a lot but it should require a torque of around 8 to 12 ft-lbs to screw in this thread. This would ensure a lot more supportive contact area and spread the shock loads. The risk of shooting this thread loose would then be gone.
Where the ideas given are really wrong is on the insistance that the metals used are no good and only stainless or titanium will avoid any deformation or bending. Nicodemus, nothing could be further from the truth. Regular carbon tool steel properly heat treated to the optimum hardness to provide toughness and springiness is easily capable of resisting the loads. And likely would do so far better than most stainless alloys and titanium alloys.
The issue with how the slot in the arbor is "tuned" on my own gun is one that bothers me as well. The metal has been peened to close the gap and then the wedge has be tapped into place to peen these upset areas back to size for a "perfect" fit. However now all the pressure from shooting is being supported by two small contact patches. A far better way would be for the barrel to be fit to the gun and then the front and back of this slot mated using a broaching action or even done by hand using a proper metal file and a jig to ensure the edges are shaped and sized exactly for a perfect mating. Then from there the wedge could be fit to the exact taper before being trimmed for the proper exposure out each end and finished off. With such a method the pressures would be supported by a much larger area of metal.
The other area that made me shake my head was again a tolerances and manufacturing short cut issue. The arbor threading into the frame is a little loose. For the sort of use we are putting this thread to the fit should be a slight interference fit so that some force is needed to torque the arbor home in the frame. Not a lot but it should require a torque of around 8 to 12 ft-lbs to screw in this thread. This would ensure a lot more supportive contact area and spread the shock loads. The risk of shooting this thread loose would then be gone.
Where the ideas given are really wrong is on the insistance that the metals used are no good and only stainless or titanium will avoid any deformation or bending. Nicodemus, nothing could be further from the truth. Regular carbon tool steel properly heat treated to the optimum hardness to provide toughness and springiness is easily capable of resisting the loads. And likely would do so far better than most stainless alloys and titanium alloys.
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