Stuck takedown sleeve.

[Hamish]

I have a couple of nice unused takedown sleeves that I bought a decade or so. When new I could take them apart, but now they are stuck.
I don't want to potentially distort them with force, I've tried to use a heat gun, and pliers to loosen the joint, unsuccessfully. Unless anyone's got any bright ideas, my next try will be with an oxy/propane or mapp torch

[superdav95]

Are they Steel on steel or brass on steel?  You could try the other extreme and use freezing.  Dry ice in middle of center sleeve to shrink it ever so slight to get it to budge.  I wonder if it has oxidation bi dong them???