Funny, but I think that the corrosive nature of gunpowder would be a problem in the machine. How about a giant helium tank that opens into a whoopee cushion until it bursts? May have to mount that outside the machine!

sledge hammer would be better

How about a nice electric jackhammer that is turned one via a relay in place of the knocker? Maybe just have it aimed at the coin door and you can rest your "junk" against the door when that special is getting ready to come around. That will get your attention.

You are not serious about doing this, right? I am sure you can find a movie prop gun that will only fire blanks that is semi-auto.

I doubt it is corrosive. I think the ramsets and most all blanks use regular smokeless powder which is not corrosive, it was the primer that was corrosive and if the stuff is reasonable new manufactured especially in the US the primer will not be corrosive.

If in doubt, fire it into a pile of random steel and copper metal bits and see if they corrode in a few days.

Honestly my best worry beyond the mechanical damage from the pressure blast to your machine is the damage to your hearing, these things are really loud in a small room without ear plugs.

Would be cool for a Russian roulette re-theme

So does anybody have any tricks for a good loud knocker? For real.

Try moving it a bit closer to where it hits. Fixed a weak knocker on my TZ. Now it makes me jump when it goes off.