How hard is it to push the shoulders back on a case to shorten the body of the case, say 1/8 - 1/4 of an inch?
How do you go about accomplishing this?

Regards
Sundowner

Not hard at all!! I just made some 7.65X53mm Argentine cases from commercial .30/'06 brass by just running them through a 7.65mm full-length die, and trimmining them to 53mm! One pass, then trim. No problem at all, but getting the lube amount just right can be a challenge. You need enough to prevent a stuck case, but not enough to cause dents in the brass.

eldeguello,
How much does that move the body/shoulder junction length back? I'm not familiar with the 7.65X53. Does it change the shoulder angle on that one too?

The shoulder angles are similar, but not exactly the same. The setback of the shoulder is at least 1/4" or so. Quite a change. the 7.65X53 is a lot like the .308, but 2 silly millimeters longer! Slightly smaller shoulder diameter than the .308!

Do not lube above where the new shoulder will be and you will not have to worry about dents.

When forming brass I remove the decapping stem.
If you then stick a case ,it is a simple matter to punch the case out.If the shoulder is moved back enough,it will be necessary to ream the neck,
I do so before the case is removed from the die.

I have one wildcat,where the neck is set back .700",no problems.

WC

Right, #Wildcat! Definitely remove the decapping stem!