Blank firing guns are easy and difficult, it's a love hate relationship.
Like one fellow said, it's just a tool but.....
Aside from the limited details that the guys have mentioned, you have to figure out the hole size of the bfa you are using, it all depends on the type of charge and where it was manufactured.
I have ran into 10 different blanks of 9mm Full flash and they are never the same load.
Keeping a detailed record of each gun for each charge from each manufacturer
Anything gas operated has to be modified.
Some blank guns will work fine firing live.
I strongly suggest that you don't do it, not only are you going to destroy the gun which equals money, but you could really hurt yourself, so I will never tell anybody how to do it, so don't ask.