Most of the U.S. doublegun makers designed some form of barrel loop support/reinforcing wedge

Hunter Arms had several variants, and this was almost universally added to LRWF and guns with a BTFE

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Another simpler support

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Parker, from "The Parker Story"

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Lefever D

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Folsom Paragon crossbolt Paragon ejector

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Even lowly Crescent had a crude support

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