Reducing number of No.4 Barrel grooves to speed production?

[muffett.2008]

Certainly brings back a few memories, I remember straightening a L1A1 barrel using the shadow method and the tow bar of a Landrover, it had been run over, a couple of test rounds and another happy digger.
I tried to save the young blokes from a severe A..Kicking, no one did it for me though when I was in Anti Tank, forgot to secure the front barrel lock on a 106 Recoiless on a Landrover, took off and so did the gun, a slow motion backflip with me trying to stop as I held onto the barrel, being lifted out of the seat.....feet off the pedals, it took only minor damage, knocked the scope a bit, but with a bit of judicious packing and bore sighting, it outshot the other guns on the line the following day.......the Gods really do like me