It sounds like there are no measurements for plastic deformation in between proof shots. That is an excellent opportunity for the original load to cause a plastic deformation and the second load to destroy the barrels. It might cost a few dollars more, but it would save some guns to measure in between proof loads. I think every person submitting a gun for proof would be glad to pay the extra amount for the possibility of saving a gun.

It sounds like the Brit proof houses are trying to get in line with Euro proof houses. They should know better. They have been getting appropriate eresults for a long, long time...until now.

On the other hand, if the two failed Purdeys were NEW, something is amiss still.