Hello Jeff

you might have a 9x57r/360
this case is based on the 9.3x72r
this case has a slight shoulder.
I have a 8x57r/360 which uses the 9.3x72r case shortened and necked down to .318 for the 8 mm bullet and the cases have a shoulder. since you use a .358 bullet the shoulder would be less.
do a chamber cast then you will know exactly what you have.
doing a chamber cast is real easy. any questions I will glad to help.
ralph