Vern, the 35 degree shoulder will lengthen the case body and shorten the neck, even then the neck/shoulder juncture on the 35 Brown Whelen is only .021 thousand different when measuring from the head of the case to the shoulder juncture, that is about the same difference between the 30/06 and the 30/06 Ackley Improved, it is said there is not a head space issue when firing 30/06 cases in the Ackley improved because the neck is shorter on the 30/06, the neck is sized when it is chambered and forms the rest of the case when fired.
This means the extractor does not have a lot to do when firing Ackley cases, back to Hatcher and his modified chamber, he moved the shoulder forward .080 thousands and fired 30/06 cases, the case head spaced on the extractor groove, his method could be tough on extractors and again 8mm57 ammo has been fired in an 8mm/06 chamber, if anyone took the time to measure that is .127 head space, others have fired 308 W in a 30/06 chamber, that is .388 head space if no one considers the 308 wedges into the 30/06 chamber at the shoulder because it is .011 larger in diameter than the 30/06 when measured from the head of both case to the same juncture on the case.
When forming 8mm Gibbs the body/shoulder is formed .202 thousands ahead of the 30/06 case body/shoulder juncture, and that is the reason I explained how and why I would neck the case up and then size the neck to get it where I wanted it.
I did not say I would not do it another way but if I had to explain why I would not fill the case with cereal.....
It is not possible to have it both ways, the standard thinking among relaoders is,... the firing pin strikes the primer THEN the shoulder of the case hits the shoulder of the chamber and in their thinking they never add time as a factor but their logic says the firing pin drives the case forward.... then we have to add another event to the firing pin drives the case forward, the added event would be the case extractor groove head spaces on the extractor....
I do not use reduced loads as in fast powders because of the rapid expansion of the hot high pressure gas, the rapid expansion of the gas has to be violent and I am not convinced the rapid expansion of the case is good for it.....I form first then fire and I am a big fan of reducing all that case travel.
F. Guffey