Can a model 411 40S&W be converted to 9mm?

Yes but...

Not with the 411 slide on there. the breechface is too wide and the extractor will lack sufficient reach to bite into a 9mm case rim.

You need a 9xx or 59xx top end assembly to make it work. Watch the auction sites for parts kits. And magazines of course.

Cheers
Bill

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Because they don't make a .46

And after you acquire the 9mm top end, you will need to narrow the base of the 9mm barrel to get it to fit the 411 frame.

Still worth the effort?

John

It can be done with enough money and modifications.
Advice from old guy who has experience , cheaper and most reliable route to go .
Save the 40 S&W...it's paid for, who knows you might need it for something . My Dad would say it's not eating any hay .
Buy the 9mm of your choice.
Conversions always seem like a good idea...until you have issues like failures to feed, fire and eject...reliability stuff !
Gary