Neck size?
I see that on benchrest rifles, the chamber neck size is sometimes stamped on the barrel. A 6ppc I am looking at is stamped .262". My question is what would you try for as the perfect neck size on your loaded case? My guess would be as close under as possible, .001" maybe? Any hard data on this one?
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bluechipx,
I've read many top benchrest gunsmiths say .003"-.004" chamber neck over size to the neck on the case. Yes, the room needs to be minimal. But there still needs to be some expansion.
A somewhat different example is my 6mm-.284 with a neck size of .282". After sizing down 6.5-.284 cases the neck thickness grew. I have .277" OD with the bullet stuffed in the case. Which leaves .005". This is a good fit for a long range rifle. Maybe tighter would be better but with having to neck down the cases for it, it means I don't have to turn necks. Just size them on a mandrel.0 -
.001 is too tight. That only leaves .0005 around the neck for expansion of the brass to release the bullet. This will result in higher chamber pressure. You must start with reduced powder levels and check for pressure signs when the clearance is small. Brass for a .262 neck must be neck turned to .0085 to give a loaded round of .260. You must use a good ball micrometer, dial caliper and neck turning tool. Since benchrest chambers are cut to tight dimensions, the neck size is inscribed on the barrel to prevent using tight brass. Most factory brass runs .011 to .014 neck thickness. 0
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