Yes its interesting opening up these old beauties. Just done one now I had been saving up as a Christmas treat - action has been soaking in diesel for a day or so. Piston washer had detached and turned into a coal like, compacted black layer wedged in end of cylinder. Rest of gun was packed full of grease. Diesel got the washer out - fortunately it had a spangly smooth compression chamber with no scoring
Been scrubbing barrel out with a bronze brush and Hoppes no 9. So much sludge is coming out I might try hot water and some Youngs 303 - a fouling powder remover....just for the smell as much as anything

The end of the cylinder not flexing is critical to these old rifles - especially the 45" ones. Quite often they have fractures - Its hard to see how wear can occur on the cylinder threads - possibly by rough handling and forcing in powerful springs. Or shooting with loose trigger screws. Probably the only weakness on these rifles. You hardly ever see component failure.