stainless steel hardline

my question is..i have stainless steel 3/8 od and i wanna use a  union fitting to join some lines together..im my town its hard to find the proper  swagelok or parker fittings designed for this line..is a brass union suffeint from like copper 3/8od pipe or will i lose air and possibly damage? thanks for responding

NOPE! the brass is too soft and wont seal or crimp on the stainless tubing

well sweet thats all i needed to know thanks bro