digitalimages wrote:
Is this a dyi job to replace the well worn mount on a 300 F2.8?
Four screws and off and on?
Is this the non-IS version? There is a slight difference between the mounts on the IS and non-IS versions. Putting an IS version on the non-IS version will make the non-IS lens not focus properly. There is a slight difference in the thickness. I had my non-IS 300 f2.8 lens mount replaced recently and Kurt's (San Diego) Camera Repair ordered the 300 f2.8 IS mount and then reduced the thickness to the non-IS version and it works great on my non-IS 300 lens.
I got the replacement part form Canon Canada, took the existing mount off (easy) and found that the replacement part is much thicker than the orginal and takes a different inside plastic barrel. This is the point where I gave up and put my lens back together. All is OK.
It seems that Canon has had two different replacement mounts and you have to machine the last version to get it to fit correctly (as mentioned.) A replacement part should be the same dimension you would think?
I have got the parts drawing from Canon and have found the part number for the mount. It should be easy....if the part is still available 
