From: megatek!hollen@uunet.UU.NET (Dion Hollenbeck)
Newsgroups: rec.guns
Subject: Re: Neck Sizing of Brass
Date: 6 Oct 92 19:40:19 GMT
Article-I.D.: peg.HOLLEN.92Oct6085224
Organization: Megatek Corporation, San Diego, California

#>>>> On 6 Oct 92 11:16:43 GMT, hes@ncsu.edu (Henry E. Schaffer) said:


Henry>   Just an example of how small tolerances can be, and the choice of
Henry> resizing dies.  I've been neck sizing my brass with Lee Collet Dies,
Henry> and have been very happy with the dies and the performance.  However
Henry> due mostly to the discussion on the net I got the idea that I should
Henry> try Wilson dies.

Henry>   So I ordered a Wilson neck sizing die for .222 Rem.  This requires
Henry> ordering a bushing which does the actual sizing, and one must give
Henry> the inner diameter measurement for this bushing.  I followed
Henry> the (Sinclair) catalog instructions, took the only loaded ammo I
Henry> had, measured the neck and ordered a die 0.003" smaller.

Henry>   It came, and I rushed to use it - resized a case, placed a bullet
Henry> in the neck - and it fell through!  What?  It turns out that the
Henry> case I measured was from one brand of brass, and all the empty brass
Henry> I had was from another, and this other brand was about .002" thinner
Henry> in the neck.  This isn't much, but it is too much!  Grrr!

Henry>   Since the Lee Collet Dies work by putting a mandrel inside the
Henry> neck and then pressing the brass down to the mandrel - the case
Henry> neck thickness doesn't matter, the neck will be sized correctly
Henry> regardless.

Henry>   Oh well, I hope that (with the new bushing I've already ordered)
Henry> that the new dies will improve my accuracy.

Well, IMHO, probably not.  Since you read the Sinclair literature
carefully, you should remember the section on neck turning.  To get
the full effect of Wilson or Jones neck sizing dies, you MUST neck
turn your brass.  The main point of these dies is that they take a
bushing of a known size and squeeze the neck down to that size.
Depending on how work hardened the brass is, it will spring back from
.001" to .002".  If you have a perfectly round bushing squeezing down
the neck which is of uneven wall thickness, then the inside of the
neck is going to be "lumpy".  wherever the brass is thicker, the neck
will be smaller diameter.  Now you put a bullet in this uneven neck
and it is gripped with .001" of tension in one place and .003" of
tension is some other places.  You are no better off that when you
used you regular press dies, except that in the Wilson or Jones dies,
the brass is better supported during the sizing and bullet seating
operations and is not work hardened over its entire length by repeated
firing/sizing operations.

To get the full benefit of these dies you are going to have to start
neck turning your brass.  Just follow the directions and take only
enough brass off to just clean up all of your cases.  This will
usually result in a neck wall thickness of about .010 or .009 for
cases in the various .22 or 6mm calibers.  

The most important effect of neck turning and neck sizing dies is that
the combination tends to produce cartridges with more concentricity
than a standard press and full length resizing.  You want the case to
be held firmly in the chamber and the bullet to be positioned in the
exact center of the bore so that as it leaps out of the case and into
the throat, it will not be deflected to either side.  Without neck
turning, this will be very difficult to achieve since the lumpiness of
the inside of the neck will cause the bullet to not be seated
concentrically with respect to the case.
-- 
Dion Hollenbeck       UUCP: {uunet, ucsd, sun}!megatek!hollen
                      INTERNET:            hollen@megatek.com
Megatek Corporation  9645 Scranton Rd.  San Diego, Ca.  92121