Fear not DRP or Chosenman. But the facts are this. No L42 or L39 got out of the factory using a No3 bolthead (the b/h). I know that there are others more versed in the art than me that will say they did, but believe me, they didn't. The only place a No3 b/h was acceptable was at unit level. If it got to a Field workshop with a No3 b/h, they'd move heaven and earth with stocks of No2 b/h's - given the large variations in length, over and underturn to send it out with the correct CHS AND a No2 b/h. If not, it was the chop. Why sell a restored car with 100,000 miles on the engine?
There was never a No4 b/h in UKMilitary service. They have been noted BUT there was Never a No4 in the parts list, EMER or the intermediate wartime SAI's issued to quartermasters. It is correct that some rifles were allowed to pass into service with a specially ground 00 size b/h. This was a factory acceptable relaxation for those tight bodies that otherwise passed all of the factory specification/standard
As for selectively fitting barrels to ensure that the rifle went out with a 0 b/h........ all I can say, rolling my eyes skywards in despair, is this. Just think about it........... In short, you'd need barrels in the system to cater for bodies that would exceed the 3 b/h size too. NOPE, just one barrel and chamber spec if you don't mind - please!!!!! You can't fix a clapped body with an oversize barrel.
A minor correction here if you don't mind. Generally speaking, the sniper rifle was a one man dog and it stayed that way for obvious reasons and in my experience, the snipers could tag on to a shooting detail at a unit range day just to keep his/their skills up so at the unit levels, the rifles never really got flogged to death. I know that they'd allow others on the range day to use them for interest or farmiliarisation and all that but really, it was to chuckle when the novice smart-arxe NCO who knew everything was showing off to the blokes and split his eye while he did so - to everyones amusement!
But if at unit level, something went wrong with the rifle, it was generally two things (plus a third but not too common) that the Unit Armourers were required to send it into the Field or Command workshops for. And that was loose front pad or loose block band foresight. In these most common cases, by tacit agreement between them, the rifle went in on its own, less the CES, to be repaired. This was because once the faults were fixed (you'd do both at the same time anyway), the rifle had to be zeroed. The re-zeroing would be so minor that it could be done by the sniper! In any case, when ANY sniper rifle was returned to a unit the 1045 was endorsed with 'SNIPER RIFLE - TO BE FINALLY ZEROED BY THE END USER' or ZEROING IS THE RESPONSIBILITY OF THE END USER. So fine zeroing would be done by the sniper as a good excuse and authority to tag onto a range day with his pal for some pretty-well unsupervised 'range practice' .
Inaccuracy was down to the poor quality of the fore-ends and when these became 'dues-out' ('temporarily' out of stock big time!) then the rifle was BLR/Z and returned to Ordnance and a replacement was issued
From this, you can see that in my opinion the same rifles stayed with their same home units for a LONG time. And if the regiment was posted to, say, Germany, they'd take over the weaponry from the unit they were taking over from and so on*. Obviously at the different training centres where the snipers were trained and tested, the rifles there were shot to death and the attrition rate was pretty bleak as you'd expect from vehicles used in cross country driver training.
I should clarify a small point and I know it's a tad academic but when a rifle, let's say our L42 is inspected at workshops and a fore-end or something else is NLA or Dues-Out, then the rifle will go back to the unit as Z-BLR**. It would not sit for more than a couple of weeks at a workshop awaiting spare parts believe me..... The Z-BLR paperwork would be the signal and authority for the Quartermaster to demand a replacement from Ordnance. The replacement issue would arrive at the same time as a 'calling-in notice' for the Z-BLR rifle which would be packed up and returned to a RSSD. More to it than that of course but notice that because the rifle is Z-BLR, it'd be set aside for repair at a later date. A good example of this is shortly after the introduction of the L96's that were withdrawn, L42's were rebuilt where possible and retained '........pending'. Luckily for some current L42 owners, new brackets were obtained to rebuild these otherwise soon to be scrap rifles. Whereas a rifle sentenced Z-BER for beyond economic repair for, for example, elongated/knackered front pad screw holes would go straight for the chop.
*not absolutely correct of course, depending on circumstances
** and Z-BER usually stripped of anything useful and shipped back to Ordnance. Plenty of these stripped heaps of sxxx were sold off, believe me!