This, like other posts about sleeving, tends to show that monobloc is the best barrel construction method to date.

Replacing tubes in a monobloc gun returns it to new condition. Can't say that about sleeving no matter how well it was carried out.

And no, sleeving is not the same thing. A monobloc breech is designed from the start to receive tubes so that the mating surfaces at the tube step are of equal thickness all the way round. Think about this detail regarding sleeving.