I am not experiencing case separations or split necks in rifle cases.
I am sizing with Lee collet dies or Lyman 45 rifle neck sising dies.
I use a 3o8 win chester neck sizer in most 30 or 303 caliber rifles because it has the largest diameter available.
In 375 H&H and 35Whelen I use Neil Jones neck dies in a press.
In straight walled pistol cases the Lee carbide dies resize the cases the minimum quantity necessary.
Lee can give you smaller diameter dies if you need them.
Ed Harris does not use the sizer die,he uses only the so called factory crimp die to size the loaded round.
I had some case failure with nickeled cases in 45LC peacemaker clones,but I think that the problem is the variations in chamber thickness in that antique caliber.
38,357 and 44 brass in non magnum loads ,cast bullet shooting with pressures last indefinitely.
I have some norma brass that I bough in the eighties and always shot wit cast in my 03A3 and USMOD of 17.Never had any need to trim them.
Case failure comes from too much full length sizing,pull through neck expanders and following the die makers manual of instructions.
Those books are are written to make you buy unuseful gadgets and case prepping tools ,and to avoid complaints as ” my cartridges do not chamber easily “.
Buy the best new cases available.instead.
Most long undersized nose rifle bullet moulds are designed to chamber easily,not for accurate shooting.
Setting dies and moulds right for the individual gun is not feasible in mass production.
PS.
Semiauto rifles in 308 or 762x39 or 223 need a different approach they are to be sized a little more aggressively, otherwise they might shoot out of battery .