singleshot

The Super and .40/10mm rims are only about .020" difference. Super barrel in my .40 slide works a treat.

All you need to do is get a 38 Super barrel and mags to go to that caliber. Probably a lighter mainspring too.

Maybe it is just me. but that primer appears to be seated way too deep. Can you manually decap it and see if it even has an anvil?

No problem with a cast bullet, but don't know how the coated ones would hold up.

I tried some today in my Witness Match 38 Super- used the 357 HP 125. Shot about the same as Hornady XTP 125s, but need to do do a lot more development on the loadings.