The temptation is always there to "test" fire a new to you pistol or rifle. Problem is that if something breaks on an all matching piece, it won't be all matching again as the part needs replacing. I know people who have done this with matching Lugers, P38's and K98's. They are only all matching once. The problem with the P38, as was pointed out by MrFarb, is an inherent flaw in the slide design. Depending upon the amount of action these rigs saw during the war, the metal may be fatigued enough that the next shot will cause a catastrophic failure. That said I always make sure I never shoot my matching rifles and instead have a very nice mismatch to shoot. I am sorry that this happened to you and hope the repair leaves it an excellent display piece for you.