fnbrowning: I don't know the answer to your last question but on two of my Winchester Big Bores with 3/4 length magazine tubes, there is a dovetail slot cut into the bbl in which a threaded keyway is fit. Into this is screwed the magazine tube end cap retaining screw, er whatever it is called. I do not know how this affects accuracy. Also, the barrel bands on my Winnies all seem to have some room for barrel expansion between the top of the barrel and the underside of tthe top of the barrel band, so I think I'm pretty ok in that regard. After reading Kelly's article I wondered if a small neoprene washer, like the ones that come with the sling swivels to place twixt the swivel screw and the stock might not have the same effect, if the screw was not tightened all the way and locktited. That way you wouldn't have all the different pressures Kelly spoke to right at the end of the barrel.
Also, on the Winchesters, the slot cut into the bottom of the barrel that allows the barrel band screw to pass twixt the bbl and the mag tube is generous enough to you would not expect pressure on the bbl to result.
I'm currently working on a Winchester Black Shadow in 444 - I'm replacing the awful plastic stock with a wood forestock from a traditional rifle and a rear stock from a Timber Carbine and was concerned about the affect of two machine slots in the bottom of the bbl - one for the barrel band screw and the other for the dovetailed mag end cap retaining screw. I will run my concerns past my gunsmith to see if he recommends filling those cuts so as to reduce a possible 'vibration' effect, er what. After all that I plan on firelapping the bore as per Beartooth Bullets and see what kind of accuracy I can get from that rifle. This isn't going to happen immediately but I will let ya'll know what it is like when finished. Mikey.