On 2013-03-04, Gunner wrote:
On Mon, 4 Mar 2013 10:12:53 -0800 (PST), "
wrote:

On Mar 4, 9:47*am, Ed Huntress wrote:


I think he's overly worried about taper. He shouldn't have any
measurable taper over that short stroke. If he does, he has bigger
problems with that lathe.

--
Ed Huntress

I also think he is overly concerned about taper. I think that taper
is a non issue. If the die has a lot of taper, will it make any
difference? The lead will be the size of the smallest section of the
die.


Dan

Taper does indeed make a huge difference in the application. Most
bullets are aprox .001 bigger than bore diameter. Squeezing it into
the bore means it becomes squeezed by the rifling and it tends to
spread in the grooves and be impressed by the lands.

[ ... ]

Now if the taper was small at the bottom of the die and big at the
top..we may or may not have a good bullet flight. If its small at the
mouth of the die and big at the ass end..its going to rip itself up as
its being sized, then slightly compressed, expanded at the bottom of
the die, and then ripped yet again as its being pushed back out of the
die. We are talking only a thousanth or so..yes indeed..but a good
bullet is now badly damaged at those RPM ranges and wierd ****
happens.

So the bullet does not simply pass through the sizing die? (I've
always used jacketed bullets.)

If it did pass all the way though, it would simply take on a
diameter corresponding to the smallest diameter of the die -- no problem.

*However* -- if you use a toolpost grinder to make the bore in the
die, you should not *have* a taper, as long as the bed is straight and
not twisted. Yes, that skinny little stem holding the point to the
grinder might deflect a bit on the first pass, but if you "spark out"
you should have consistent diameter even if the first pass is not that
good.

The main concern with using the toolpost grinder is properly
protecting the ways and other sliding surfaces from the grit. I've so
far used mine *once* (so far) -- but I *will* use it when it is the best
tool for the job.

Enjoy,
DoN.

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