While out shooting yesterday I noticed something interesting. My M65 has a longer cylinder than my M651. So I thought I'd post the numbers for others here as a point of interest.
M65 357 magnum (medium frame, 4" barrel, blued): 1.635"
M651 357 magnum (small frame, 2" barrel, blued): 1.565"
M85 38 special (small frame, 2" barrel, stainless): 1.51" (just for reference)
All the measurements are a rough average of numbers taken a various points around the cylinder.
When we noticed this we put a 357 magnum 158gr JSP in for a visual reference. There was a definite difference in available space. I don't have any 180gr loads around to try and see how they look.
I'd guess that the only time this could cause an issue is with a heavy bullet that has started to pull out of its case due to recoil. Remember that it doesn't have to be just the rounds you've previously fired from that cylinder if you have had that particular round in the cylinder previously and fired the others (say 2-3, not necessarily 4-5) and put it back into the box for later. No, I have not had this issue with this, its just something I've read about.