Hi Ed,
Have a .22 45" Imp mod D with similar fractures to the cylinder just in front of the trigger guard, though no where near as bad, they are just hairline cracks.
I reckon its from it being repeatedly cocked with the trigger guard screws loose over the years. Not by me I would add.
Is it weldable do you reckon and what type of welding would it require. I might try and get it done locally as my van also needs some welding and I could use a bit of info.
Cheers Morgan
"helplessly they stare at his tracks......."