Well, so take it all outside. Then it won't boil off quite so fast......Don’t forget, though, that Muddy is working in his Basement! Propane - NO Way!
Well, wait, maybe all he needs to do is take it all outside, and leave it there overnight. No propane required......
The propane A/C refrigerant idea mostly scared me from the perspective of an auto accident where fire might be involved and the unsuspecting firemen.
The CO2 from the dry ice can be a breathing hazard as I'm sure that you know.
I think that I have the same action wrench. That bar behind it with the shouldered threads on one end isn't a barrel, it is the lever for the wrench. There is a hole in the 'cap' (barely visible in the pic) for such an action screw.
Not long ago I built some AL pillow blocks for a road racer's front sway bar. The way that I built them was to buy 1.25x1.25 6061 T6 bar-stock and cut the lengths that I needed. Then drill all of the mounting bolt holes. Using a steel dowel pin in each pair of holes to align them I clamped them sideways in the vise and hole-sawed the bores slightly under-size and then bored them to size. Made putting the center on the split really easy. I could see doing this with a thick shim (.03"-.06") of some sort between the blocks to make some AL barrel blocks that can't go to zero on themselves.
I made those with a mill, but I have made similar parts by abusing the heck out of a tool like this: https://www.amazon.com/General-Tools-55-Cutter-Adjustable/dp/B00004T7OZ in a drill press with the work securely clamped in place.