It will indeed hit the baffles, but not the shutter. If you do it often enough you will scar the baffle. Just leave it fully extended and locked and there is no pronlem. In the days of the Leica M5, leitz recommended that you run a strip of Dymo label tape around the lens barrel to prevent it from fully collapsing and fouling the meter arm. You can use the same trick with the Bessa/Canon.
If my memory serves me right(it seldom does) some of the very early canon lenses had a slightly different thread pitch than the leica ones. If this is the case, be careful as it is easy to "cross thread" an adapter or mount and you end up with a permanently mounted lens! I suspect that someone on the Forum can enlighten us more on this, please.
