Well heres the article on wandering zero I mentioned earlier
you could always tell the high mileage rifles, apart from the shot out barrels because the back sight axis retaining pin.....was always sheared where the the bodies had expanded at the rear and sheared it.
According to Reynolds "the Lee Enfield Rifle" they investigated the possibility of poorly seasoned wood causing the shift in zero and found that was not the cause.
The linseed oil soaking of the SMLE and earlier Enfield stock sets seems to have been sufficient to prevent warping due to moisture, and those rifles and their stocks are far more sensitive to shifts in bedding than a short fee floated barrel would be.
The shims I mentioned were used to fit No.4 MkI* L rear sights.
During MkI* production many rifles required refitting and substitution of parts, the rifles often not being up to snuff when first delivered, and substitute standard parts were often out of specification.
Most if not all that had out of spec parts would have been repaired shortly after delivery or during rebuild programs years later.