I know what a metronome is, and I understand the concept of developing a repeatable rhythm to the casting process – But I think this may be getting a little too far into the tall weeds.
If you open the sprue plate too early, you will smear molten lead across the top of the mold and the bottom of the sprue plate. If you let the sprue cool too much, you will need a little more force to cut the sprue as you open the sprue plate (probably not the end of the world). Your brain is capable of dealing with that input and adjusting the speed to fit the process. In fact, it is capable of doing that on the fly and constantly adjusting the timing as the temps change.
The temperature of the alloy is going to be a bit variable. The temperature of the mold is going to be very variable at first, but it will settle down as you get farther into the casting session.
Adding a metronome to the process, whether it is a mechanical musician’s device or an electronic timekeeper, is just adding yet one more damn thing to fool with while casting.
Sometimes you just need to say NO to the good idea fairy.
You are going to have a pot of molten metal within some temperature range.
You are going to have a mold or molds warmed up and hopefully operating within some temperature range.
You are going to have a mallet, stick, whatever – to open the sprue plate.
You are going to be filling the mold(s) with a bottom pour pot or ladle.
You’re going to be constantly changing your rhythm and timing until you match all of those temperature swings to achieve good bullets.
You are going to be dealing with finished bullets, sprues and cold alloy.
And now you want to add some ticking device to the process ? No thank you. I’ll make it all work without the additional complication.