Odd shaped 10mm?

[YouKnowDamnRight]

Got some brass and some of it was a bag of 10mm. This doesn't look like 10mm to me though with the tapering. Slightly fits a 9mm bullet in there. Are these useful?

 

[BamaFaninMilton]

Looks like someone was trying to create a wildcat of some sort.

 

[Norm]

I’d guess they were trying to neck down to 357 sig.

 

[wildrider666]

Its probably 9×25 Dillion.

 

[Gunin4m]

Agree with Wildrider, definitely looks like 9x25 Dillon... Making cases out of 10mm brass used to be pretty common...

 

[Jdcujo]

9x25