The British typically shot with a straight L arm, holding the barrels, and erect head position

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"Capt. Jack" Brewer; a pre-1900s top Pigeon shooter

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Helpful images from the DuPont Grand Smokeless Championship Handicap Live-bird Tournament, 1895
https://books.google.com/books?id=DkMhAQAAMAAJ&pg=PA413&lpg

The Top Guns did what worked best for them, as do the Top Guns today. The shooters were in the 'ready' position so several had their heads up, but all look to be holding the barrels, or possibly a barrel guard

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Southern Quail hunting 1906. Crawling the stock with an exaggerated forward lean and straight L arm

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