I have to say I would be very wary of relying on the old wives tale that you can shoot the gun on the odd occasion for 'test purposes'. I have a couple of original revolvers including a .44 cal Remington that was fired by the previous owner but most of the local MLAGB competitions insist that the gun used is on your FAC, certainly any of the International competitions would insist on this. Whether or not you would need to have it proofed to do this is a question I can't answer but no doubt someone better informed can tell you. The only thing that might make a difference is that it seems almost all Firearms Departments interpret the rules differently, well, Thames Valley definitely do....
Just out of interest, I owned a .36 Remington Uberti reproduction and despite some serious work it wouldn't group to save your life. Needless to say, it's no longer with me