The procedure you are asking about is usually used when a firearm has excess headspace. The case is necked up
and then partially neck sized back down to its original caliber. When necking down its done in steps to create a shoulder on the case so that it actually chambers with feeling or a crush fit. Upon firing the shoulder and the base of the case are longer to make up for the excess headspace. Frank
I agree, the Lil 35 has a problematic "weak" shoulder and can be a problem is some actions... What is the firearm? What is the brass?
Marlins and bolt guns for example generally will be just fine as the extractor will hold the case against the bolt. Effectively forcing zero headspace. (Without regard for chamber dimensions) While handis for example will be greatly effected by the small "weak'' shoulder. Accuracy may suffer on first shot...
I have found Rem Brass to be quite soft and problematic for this. Once fired a couple times its now "work hardened" and better.
Are you experiencing any problems?
CW