A persistent magnetism is caused by repeatedly using magnetism in the same direction to propel the iron. Here are some ideas:

If this is a spring return device, you might reverse the polarity of the current at every other stroke by using an H bridge or some clever mechanical switching, or just reverse the coil connections by flipping a DPDT switch with your fingers every 10 minutes.

Another way would be to degauss the iron with something like a bulk eraser that was designed to erase VCR tapes. This would be unacceptable if you need to disassemble the machine to degauss it, and it would surely be annoying to stop every ten minutes to degauss the machine while you're working.

If the switching is simply mechanical, you could reverse the polarity of the DC power supply every ten minutes. This might even work if you use AC instead of DC current.

I think the DPDT switch is a likely fix, but if you can run the machine on AC, that would fix everything and require nothing from you in the future.

Just tossing some ideas in there.

 

Great, I'll definitely be looking into those, thanks! And they are ran off DC. I didn't think they could run off AC, just due to consistency/stability issues... idk. This has been quite the rabbit hole.

Just curious, but would you have any idea to as why this just suddenly started occurring after so many years?

 

Somebody changed something, possibly the alloy used for the moving part is different and accepts residual magnetism better. I suck at metallurgy, but somebody said just today that low frequency transformer iron is designed to not retain magnetism, so it's possible one unknowing person ordered the wrong steel.

I'm rather curious about the idea that a solenoid can be run with AC if it's the right shape. That remains a possibility in my mind.

 

Maybe a dumb question, do you have your breaker points on the gun set correctly? Are they oxidized?

 

yeah the contact points were sanded down and the point gap is basically how i would fine tune the machine and its still just off enough to run smoothly or with enough force