After much searching I finally found a qoute from a reputable source about the strength of the Browning High Wall in 45-70. Chuck Hawks of "Guns and Shooting On Line" states the following;

"I handloaded the 500 grain Hornady Interlock RN bullet to a MV of 1750 fps from the 28" barrel of my .45-70 Browning High Wall . The pressure of this load is such that it is safe for use ONLY in strong, modern single shot rifles such as the Browning High Wall, Ruger No. 1, and Dakota 10. My Browning delivered excellent 100 yard groups with this load, and the big 500 grain .458" bullet has an exceptional SD of .341, so I wasn't worried about adequate penetration!"

Chuck Hawks also states in another of his articles on the 45-70 cartridge that this "strong action" found in the Ruger No. 1 and Dakota 10 can handle pressures of approximately 50,000 CUP. He did not mention the Browning High Wall along with the Ruger & Dakota in this latter article.

Any comments are welcome!