Saad, Hi.
Where are you?
This sawing the bbl off just before the rupture & welding on a length cut from another waste bbl sounds a bit iffy to me by your description.
Sleeving is basically cutting of the bbls just ahead of the chambers..about 4" or so ,boring out the short chambers/bores,
then turning down some tubes for a 4" stepdown that is seated into the newly bored chambers.
I'm sure I'll get some flack for my description.
Your way, seems like hes gonna try to weld two bits of bbl together with a circular weld around the bore....that doesn't sound like fine gun repair to me.
Perhaps I'm miss understanding.
If you go to the Gunshop home page...find John Foster UK in the advitizers drop box...he shows how he sleeves..& hes good at it .
cheers
Franc