KF-NYC, thanks for the comments. I haven't had a chance to check the forums for a couple of weeks so I'm sorry for the late response.
The weight of the 640Pro makes it easy to shoot anything up to 158gr +P loads for me. The magnums are a handful, though 110gr magnums aren't too bad for about 15 shots or so.
As far as the difference between the barrel lengths of the 640Pro and the 60Pro Series, I'm not sure. Velocities will vary with each individual gun, and could be really close or significantly different depending on the specific guns tested. I would expect to lose somewhere between 25-50FPS with the shorter barrel compared to the 3" barrel, but that's just a guesstimate. I did some research on what works in short (1 7/8") barrels and came up with the FBI load (158gr+P LSWCHP) and the Speer Gold Dot short barrel loads (AKA the New York Load I believe, 135gr+P JHP), so those are what I use. The FBI load hits closest to point of aim, so I stick with that as much as possible. I was using Remington but I understand that they watered the load down when they changed packaging and upped the price, so I'm going to Buffalo Bore when my current stock of older Remington runs out.

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