neck size.....bbl marking vs fired brass

M

mike in co

Guest
gentlemen,
i have a 30 br bbl that is marked "330 nk"
i just fire formed a new lot of brass and it all measured 0.331 .
question: do you think the neck is actually 332 ?
how much spring back does new brass have ??
this was fire formed with fast pistol powder, no bullet, no wad, pure powder.

as a clue to maybe not a "great" chamber, the brass must be resized or it will
stick in a wilson seater.

this is the third hand kreiger bbl that i have mentioned elsewhere.

the more i learn about the bbl the more i lean to cutting off and starting over with my reamer.( see my reamer thread)
 
For my 6PPC barrels, that have .262 necks I have observed that fired cases' necks (turned, unannealed) come out of the chamber about .001 smaller than the chamber neck's specified ID.

In the past, with much thicker necks, from a factory .220 Swift chamber, looking at various manufacturers' brass, I have seen a lot of variation in this dimension from the same chamber, which I took to be an indication of differences in case neck hardness.

If you work with a single case and gradually reduce its neck thickness until a dummy round barely chambers I think that you can get a pretty good fix on your chamber's neck ID.
 
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