Rust Slug

 I've heard many times about all the steel shot in a shell rusting into a slug, then someone blowing up a duck or goose with it.  I find this pretty hard to believe: rust is a pretty weak adhesive, and the actual surface area of the shot in contact is pretty small.  Generally, when two pieces of metal are rusted together so tightly they don't break free with a mild blow, it's a situation like a nut and a bolt--two tightly fitted pieces which are SUPPOSED to adhere to one another anyway.     

I've never seen a photo of a rust slug or any other evidence beyond stories.  But I refuse to call anyone a liar--I wasn't there after all.  Besides, how can I prove it could NEVER happen?  

So in good faith, I'm going to try to create a rust slug.

3.23.25

I started with seven Federal Speed Shok 12 ga 2.75", 1.1125 oz #2's.  All had a gentle rattle to them.  

A buddy gave me these about eleven or twelve years ago when he moved, and they'd been bouncing around in various ammo boxes for several years before that.  I set one aside as a control.  I opened up the other six.

Here's the shot from one of the shells--all nice and shiny.  I dumped the shot into a saltwater bath.  

I did not measure the amount of salt, just poured in what felt good.  Maybe an 1/8 teaspoon in 2 oz of water?  After soaking for a 30 seconds or so, I poured the wet shot back into the hull and recrimped.

I then set the shells (except the control, obviously) shot end down in the saltwater bath and left them there for a month.  

4.22.25

I stopped soaking the shells.  I hadn't intended to leave them that long, but merely forgot.  Though to be honest, I don't know how long it would take anyway.  

5.11.25

I carefully opened up one shell.  There was a hint of rust on the hull mouth, but none on the shot yet.  Kind of sludgy though.

I loaded the shot back and recrimped the hull.  

6.19.25

I opened up another shell. Similar results.

At this point, I forgot about this project as I started working on loads for the '25 season.  Which was just as well, because this was obviously going to take a while.  

10.26.25

Now, only the control still rattles.  So I pried open a shell, which felt a lot more solid and had way less give then a normal round.  When I tried dumping the shot, only about 105 g of shot fell out even with a gentle thwack on the head of the upturned hull.  

Now we have rust! And about 4/5 of the shot is stuck in the wad.  So I shot some paper.  I used a cylinder choke because 1) I didn't want to put extra stress on the slug beyond the firing process, and 2) I didn't want to screw up any of my chokes.  

Rust Slug #1 @ 30 yards

105 hits

As you can see, the shot did not stay in slug form.  I have 105 pellets on the 36"x48" paper, or about 70% of the shot.  There's no reason to believe the unaccounted for ~35 pellets stayed together.  But even if some of the shot stayed together or embedded into the wad, it'd hardly make a slug.  The wad didn't hit the paper (the two X's are marking tears in the paper where I dropped the staple gun on it before the shot), and much as I looked,  I couldn't find it in the tall grass.

But I have another five salted shells to go, so we'll try again in a few months.  

1/16/26

I've decide to make a rust slug outside of a loaded shell.  

I took about about an 560 g of #1 steel, soaked it in salt water all afternoon, then poured it into a CSD118.  I then placed it in a clear hull and filled the extra space with plastic beads.  At some point, I'll try cutting it out.