Honing the neck of a full length sizing die

[Clark]

Bart, I always thought that the firing pin pushes the case so hard that the bottle necked case shoulder fits in the chamber shoulder taper like a Morse taper. I was assuming that the firing pin force into the taper will not be affected by the less extractor tipping force at the rear.

The article I referenced above show that the chamber straightens out very bent 30 cal ammo so that the worst ammo all get the same 2" group.
See if I can find that.

These deviations become proportion-
ately less as the tilt is reduced. Tilts
over .O04" do not seem to increase the
dispersion of the group beyond the ex-
pected one minute. Perhaps this is
because a well-fitting chamber has a
tendency to straighten any rounds
which are excessively tilted. Other ex-
planations are possible.

I will pm the whole thing in two messages [over 6,000 characters]

Anyway, I am honing out a die right now.

 

[Clark]

I worked on a couple dies today.
I hacked off the top of a Lee 25-20 sizer die and bored out the neck from 0.266" to .303".
I wanted to neck down 32-20 brass to 25-20 in steps of less than 10%.
That did not work well as the pressure relief hole Lee drilled at the shoulder leaves a scar on the necked down brass.

So then I sawed off a chunk a 7/8-14 threaded rod and made a neck die with a .313" neck.
That is working well as a first step on necking 30-30 down to 25-35 and 32-20 down to 25-20.

 

[jepp2]

I finished honing out the die neck. I am very please with the results.

Starting neck ID on the die was .237". I needed the ID to be .245" to avoid using the expander and have the neck tension I wanted. So I needed to remove 0.008" which is a LOT given my limited tools.

It took several hours. I wasn't at all impressed with the flex hones I used. They seemed to be designed more as "glaze breakers" and lost their abrasive very quickly.

I checked many of the sized cases for neck T.I.R. and all were well less than 0.001".

 

[tangolima]

I was skeptical when I heard it would take only 15 min.

-TL

 

[flashhole]

Clark, how did you accommodate the shoulder angle when you made your die?

 

[Clark]

That was just the neck die. The necks are only supposed to change 10% per step per some wildcat club.

I have made some more dies and honed out some Lee sizer dies and one RCBS die today.


I combined some of the things from various above posts.

I sawed a slit in the dowel with a hand held jig saw. It has the narrowest blade.
I cut the emery cloth not square, but so the wrap diameter got bigger then further I pushed it in.
I wrapped 80 grit emery cloth from the slit.
I put the die in the lathe chuck.
I put a pin gauge in the die.
I dialed in the lathe chuck until the test indicator on the pin gauge runs true.
I put the other end of the dowel in the hand drill.

So I have been converting 100 rounds of 32-20 brass to 25-20, 100 rounds of 30-30 brass to 25-35, and 3 rounds 303 Brit brass to 25 Krag Ackley.

I like the drill chuck grabbing the dowel. I really hated the dowel spinning in my fingers when I lost control.