There is no rifling in the barrel of a blank pistol (why would there be?). Most blank pistols have no barrel at all in the conventional sense. They have an escape hole at the top and the rest of the dummy "barrel" is solid.
Since a blank creates almost no pressure, the guns you see advertised are made out of cheap alloy castings that will come apart if a live cartridge were ever fired in one.
There are higher quality blank pistols, like some of the German 8mm's and the old H&R starter pistols that might be worked over, but would not be worth the trouble.
Of course, there are legal aspects, as in everything else. Converting a blank pistol would be "manufacturing a firearm" and doing so without a license would be illegal.
So, considering the possibility of being in jail and missing fingers, I would tell your friends to forget the idea. If they are too young to buy a gun and think this would be a cheap way to get one, getting a little older is even cheaper and less dangerous.
Jim
