It still mystifies me that Jack O'Connor and Elmer Keith killed anything. Jack used a plain-jane 270 with (maybe) a 4x Weaver scope. And Elmer? Well, hate all you want, but he killed lots of stuff out at ballistic reticle distances with iron sighted 44 spl, 44 mag and 45 Colt. I'm sure that when Elmer did shoot stuff with a rifle he had no more than a plain crosshair to aim with.
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Jack O'Connor was quick to jump on the velocity bandwagon, though no doubt some declared that it was a wonder anyone ever killed anything with 30-30s and slow-poke early smokeless cartridges. Since he wrote chapter after chapter on range estimation techniques and their short coming, I bet he would have been the first one to grab a LRF once he got past the MPBR technique that he did more than anyone to promote.
Keith had no problem using a ladder front sight on some of his revolvers to give a vertical reference for different ranges. I'm sure he would have recognized the same principal in a riflescope.
Inovators like those two gents were quick to try the new.