Chambered Round Alignment to Bore; Neck Sized vs Full Length Sized

[BountyHunter]

Yes. All tailored to a specific chamber and desired neck diameter and tension

 

[Canadian Bushman]

"Note that pin's got between 20 and 30 pounds of force that's gonna hit the chambered round's primer."

And that force immediatly jams the cartridge fully forward into the chamber so hard it typically sets the shoulder back 1-2 thou. The simulteanous explosion of the primer through the restriction of the flash hole blows the primer cup firmly back against the bolt face; at that point, and no matter how the case was sized, the case is firmly held between the bolt and cone of the chamber shoulder.

After showing up to this party late and reading this entire thread this stands out to me most.

Whether the primer or the firing pin is putting/holding the case there, the shoulder of the case /chamber and the bolt face/firing pin are aligning the round when the bullet is leaving the neck.

In my mind the similarity between the shoulder angle of the chamber and the shoulder angle of the case would play a very crucial part in the alignment of the bullets axis to the barrel's at this moment in the firing of the case.

Two more things that grab my attention, most inherently accurate rounds used by picky shooters use aprx 30 deg shoulders and often ream their dies with the finishing reamer of their guns chamber. Two aspects i think could contribute to a cartridge/rifles's accuracy in regard to this point of bullet barrel alignment.

 

[BountyHunter]

No you cannot successfully use a finish reamer for a sizing die. You must use a resize reamer for a sizing die.

 

[Canadian Bushman]

Im sorry my mistake.