Only problem is that peacetime standards and emergency wartime standards can be very, very different..... and this is what happened. At the time of Dunkirk there were only a few thousand Number 4 Rifles in existence..... and the Army was "short" of combat rifles by about 100,000 units..... and they wanted to fill in the gaps with shiny-new Number 4 Rifles rather than the SMLEs which BSA was cranking out. So more than just a bit of pressure went into the manufacturing, added to which was the fact that ALL the Number 4 plants were tooling-up, training workers AND producing rifles at the same time. It was a small miracle that they actually got anything made, much less the damfine rifles which they DID turn out.
Let's say that they really superduper needed rifles and turned out a batch with slightly short bolts..... which NEEDED a 3 bolthead. The first replacement then would be a 4, second replacement should be a 5, third replacement should be a 6..... and the Table of Spares only made provision for 4 boltheads: 0, 1, 2 and 3.
They were TRYING, partly for the sake of simplicity, to turn out rifles which would leave the factory with as close to a 0 as possible. If this occurred, the rifle-bolt could be reheaded with a 1, then a 2, then finally a 3..... by which time the body (receiver) SHOULD be approaching the limit of its safe life.
But all bets went out the window if the rifles took a 3 when they were brand-spanking new.
In order to KEEP things simple and TRY to approach that ideal situation, every rifle (almost) was FTR at some period. In the case of rifles with bolts at their limit, a special effort was made to locate and refit ALL of them to bring them back into spec. This they VERY nearly accomplished. I have been collecting and shooting these things for 50 years now and have met with only ONE of each of the "never-produced" bolthead numbers, both more than 40 years ago.
If we have problems today, we can blame them on that nice Mr. Hitler, the fellow who offered "peace for our time" and then kept on invading his neighbours.
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