A bunch of Italians with a florist shop in Brooklyn, can you get any more cliched?
When I got the .22 AR-7, slipped into the user manual was an invoice from a gunsmith decades back. Apparently it was brought in because it was "jamming" although the gunsmith wrote that he couldn't find a problem.
The gun originally belonged to my Great-Uncle's now deceased son. He included some ammo the son used and there's the problem: He was using lead target loads instead of full metal jacket hi velocity. Of course the thing was jamming. Either the powder was too low or the lead bullet was causing it not to feed properly.
I actually took it out and tried to get it to jam with FMJ ammo and it wouldn't do it.
Unless the gun you are firing is a handmade Pakistani Makarov the problem of "jamming" isn't intrinsic to the gun itself. It's the ammo.
Even though small autos can be quirky, I'm willing to bet it worked just fine. Of course, grandpa may have had crap ammo. Unless we find the gun, or the ammo used with it, there's really no way to tell.
If the argument is "Well, it was grandpa's old .25, of course it jammed", all I can do is give a healthy "meh".