I only shoot lead bullets in my S&W M60. Remington 38Spl lead bulleted ammo has been the cleanest yet and requires only a few passes with bronze brush to leave bore clean and shiney. Have not yet fired any of Federal 38Spl lead bulleted ammo but, expect it to give same performance. Both Remington and Speer pure lead WC bullets leave no lead in bore. On other hand, I have used other factory lead 38 Spl ammo, with hard cast bullets, and ended up with badly leaded bore and VERY dirty gun.
My reloads use mostly very soft Speer or Remington 0,358 bullets, either 148 wadcutters or 158 grain SWC. Other bullet currently used is 158 grain 0,358 very soft lead SWCHPs with gas checks. The soft lead SWC bullets are loaded up to almost 1000 fps and those with gas checks up to somewhat over 1100 fps -- NO LEADING!!
HOWEVER, IF you have a gun with oversized cylinder throats, forcing cones and/or bores, you MAY get lots of leading IF hot powder gasses are blowing past bullet, melting lead and depositing it on gun. This is most likely to be severe with hard cast bullets.
Niklas