Slightly shortened barrels.......... that's switched on the memory banks. There was a project in hand regarding L42 barrels. Because they were exposed and by very the nature of the beast, they suffered constant attrition from bulges at the muzzle. 14 MAG were looking to see whether the barrel could be shortened by 'an amount' in order to save an otherwise perfect but bulged muzzle.
I think that they could be shortened without detriment for a muzzle bulge/ring but don't know how much. But seem to recall that it wasn't much at all. Another problem - if it is a problem, was that the rifle had to be unbreeched and barrel removed in order for the correct machining to be carried out.
Another problem at the time was (and I don't understand it either but may have got it slightly wrong if anyone cares to comment) that to save a bulged/ringed muzzle, you had to identify the bulge as soon as it happened then isolate the rifle before many more rounds were put through it otherwise more damage was done. In my opinion, the damage was already done but WO1 Roger xxxxxx was leading the trial and I won't be seeing him for some months now
There was another project being looked at by the 'tiffy' courses at Bordon to ascertain the viability of a slimmed down L7 fluted flash eliminator being fitted. The aim was to incorporate the two ideas as a preventive measure for the bulge problem. I think I've mentioned this some time ago. Sorry if I'm boring you!