A "sharp" magazine shot might look pretty miserable enlarged much. Heck, I once had a handheld night-time 8 second exposure of a car accident published in a newspaper. A wreck in its own right, but it told the story. What I've done with my own 300 real cannon-barrel, for the Pentax 6x7, is sometimes rest it on a jacket atop a car roof or fence post or boulder, rifle sniper-style, and shoot at a fast enough speed to avoid mirror slap until after the shutter curtain did its thing. That has worked out well in suitable cases. Otherwise, a really seriously built tripod is the only ticket. But on a good vibration-dampening tripod like a big wooden Ries, the greater mass of that big lens itself becomes an actual asset. On a flimsy tripod it would have exactly the opposite effect.
I have a high quality Nikon adapter for it too; and other than the sheer bulk of the whole setup, I suspect I get better results that way than I would with a dedicated Nikon 300 tele. Since only the center of the optic is used, even shooting wide open carries no qualitative penalty (with the EDIF version, that is; the regular Takumar version 300 is not as well corrected).
