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I have been investigating the strength of various double shotgun/rifle designs using FEA. The load I'm applying is the SAAMI rated pressure for the cartridge over the diameter of the case head (not the rim ). I realize under normal firing conditions the case grips the chamber walls thus the backthrust is greatly reduced. In comparison to bolt action rifles O/U and SxS have no where near the safety factor. In fact most exhibit stress beyond the yield point of 4140 steel when loaded per above. I'm limited by my ability to get accurate dimensions for the double rifles of today such as Searcy's other than scaling from photo's. I have made comparisons for various options such as crossbolts, side clips, double underlugs. If you have two underlugs the rear most one sees most of the load. If you have double underlugs and crossbolts, the cross bolts see the highest stress and have seen none that would not yield ( based of measurements taken from Greener 12ga shotguns ). I have taken the diameter of the crossbolt to .375" I suspect they are fitted loose to allow the rear lug to be loaded first and only used for safety. I don't like loading crossbolted actions quickly I tend to snag my thumb on them. Side clips are questionable, when one barrel fires the other barrel is pushed into the breechface as it tries to twist ( pivoting about the hinge pin laterally ), unless the clearance is excessive to achieve this. O/U designs are not necessiarily stronger. Due to the upper barrel above the hinge pin they tend to load the hinge pin harder than SxS's do. Hinge pin diameter and location relative to the breech face and barrel centerline and lug closest to breechface seem to be the most significant design variables. I have not checked bifurcated lumps but intend to do so, A friend has a Ruger O/U. 12ga I originally started this investigation as I wanted to convert a shotgun to rifle but will refrain from doing so until I can get and idea of acceptable load criteria. Any Help?????? What is the design safety criteria for such a rifle when determining the loads it should withstand thrust wise? What pressure vs. maximum should be used over what the particular cartride is rated for ( proof psi)???? And Yes I'm a LEO too. Maybe there should be a page just for us.

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Originally posted by Mickey:



Of course. The top one is a 500/465 that was made in 1912 and belonged to, among others, Bob Langevelt. He shot over 1000 elephants with it in the 25 years he owned it. The rifle was originally sold to a a person in Kenya and then somewhere else until Bob got it in Uganda in the late 50's.



I had it complerely refinished and restocked when I bought it but all of the parts were still original. The hinge pin was replaced twice by Holland. Once in the 30's and then in the mid 80's when I got it.



The middle one is a .369 Purdey. All original except recase coloured and stock refinished. Internals never touched until I sent it to Purdy to be refinished. They opened it up and stated that it had not been opened before. Made in 1940.



Bottom is a Watson Bros. Made by Holland in 1903. It is a 303 and has not been touched to my knowledge. Rifle came from India to Canada by way of a retired British Army General. He bought it from a BA Major in 1935 when he went to India as a newly commissioned whatever. His shooting book shows over 400 animals shot with it by him. Previous shooters unknown.

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