I have a lot of troubles to get 356 win brass, but I have no difficulties to find 307 win brass. Can be formed 356 brass from 307 brass?
If it is possible, Have I to carry out any special operation, (e.g. inside or outside neck trimming...)?

Thank you in advance for your advices.

i read an article about the .356 and .307. the writer said his rifle would feed and eject .358 and .308 winchester brass just fine.no personal knowledge,though.

I would think a good lubing inside the neck of the 307 Brass and running that over your 356 expander button carefully, your problem would be solved. I have also used a very nice tapered .338 Hornday expander to step brass up from 308 and then finished on my 358 expander for the Whelen.
Try some and see; maybe the above process will be all you need or you might also need fire forming for your rifle.
dmw

As Fury says, they will neck up just fine. If you have an intermediate expander button (like 8mm or .338), then you can do it in two steps which will usually result in more uniform case necks. If you can get a tapered expander that's even better.

There should be no need to trim or thin the necks, but it is best to start with new rather than fired brass since new brass will have slightly softer, more ductile necks that will more readily expand without splitting.

As M. Carroll says, your rifle will probably feed and eject regular .308/.358 Winchester brass just fine. If it will, there is no advantage to using the rimmed brass since this cartridge headspaces on the shoulder, not the rim.

I've got a couple boxes of new unfired Winchester "white box" I'd part with.

Sorry. Spain? Not certain I can ship it

Jeffeosso:

Thank you for your offer, but as you suspectted, it is almost impossible to send anything related with ammunion to Spain (including bullets) without a import permission.

Best Regards

You can form .356 from .444 Marlin cases too.