Sporterizing a few 1909's from various makers in years past, I do recall that drilling and tapping the front bridge was not noticeably problematic. Surface hardness and yield strength are two different animals. I don't think there was any surface carburizing like was found on the 1917 Enfields and those godawful Krags. Who knows where these these stories begin and how often repeated without any actual experience. (example, the short neck on the .300 Win Mag is detrimental to accuracy, right?) My personal 1909 is in the original 7.65x53, and I routinely have loaded it to .308 Win pressures for 30 plus years. The original military light ball, 150 gr load achieved 2920 fps (Ludwig Olsen, The Mauser Rifle) with powders of 100 years ago. Would I chamber a 1909 for a 65,000 psi cartridge? no. But I wouldn't blow a lot of money fixing a problem that may not be a problem.
