Why, yes. I believe so.
Urban Dictionary: eat lead
[native speaker, not a teacher]
Can we say "eat lead!" as a threat to kill somebody.
Eg. You're gonna eat lead!
Eat lead is kind of dated as a metaphor. I remember it being popular in cowboy movies and TV shows from the 1950s. Today's slang is more like, "I'm gonna bust a cap in yo' ass."
Yes, the meaning is the same: "I'm going to shoot you!"
In American slang ass has a lot of uses.
Get your ass out of here! (Get out of here.)
She has a big-ass car. (She has a big car.)
She has big-ass teeth. (She has big teeth.)
Your ass is grass. (You are in big trouble.)
I'll have your ass in a sling. (I'm going to cause trouble for you.)
His ass is mine. (I'm going to beat him in a competition.)
The list is endless.