There are literally millions of No 4s out there, still being used. However, I think I MAY know what you ran across. In about 1960, the Ministry of Defence had a test program to convert No.4 rifles to 7.62 NATO. And yes, there were enough problems with the L8 (as it was known) that they dropped the test.
The L8 is different from the Ishapore rifle that was designed and MADE for the 7.62 NATO.
Unless you are trying to shoot seven six deuce in an Enfield, I would not be overly concerned.