(Much the same as a target shooter may exactly specify what they want on the build of their rifle, down to barrel/stock/action & trigger type etc.)
Speaking from experience I know that each shooter may have started with the "standard" stock on their target rifles but then would spend a few weekends (or months) customising it to suit themselves. This would include modifying the the "bed" of the barrel, length of the stock, position of the sling mounts etc. We even had people that would create their own fully custom stock from a piece of wood (this was in the days before fibreglass moulding and Carbon Fibre).
Biting the hand that feeds IT
