4seventy,
However, concerning double rifles used for hunting, the self opening system is quite limited in usefullness, and in some hunting situations, the "one handed" gun opening method has more negatives than positives IMO.

For target shooting, club comps etc, a self opening double rifle might be ok, but for a hunting double rifle, there is not much to be gained by attempting to use the traditional one handed breaking of the gun.
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Oh, really? How is it that you come to this profound conclusion? Perhaps your "hunting situations" differ from mine, but I have found self openers to be more positive than negative in real hunting situations; a joy to use. Many barrel cocking traditional double rifles are hard to open, stiff in opening, with more negatives than positives.