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BPCR BRASS - STRETCHING OR SHORTENING
OVER TIME?
By Wayne McLerran
Posted 9/19/19

Although I’ve been shooting a Browning .40-65 BPCR since 1997, I did not
actively participating in silhouette matches until
mid 2012.  Since then, the same
200
pieces of Remington brass, which were reformed from .45-70, have been
collectively reloaded a total of 7600 times.  So each case has been reloaded an
average of 38 time so far, and none have been lost due to cracking or splitting
although the primer pockets of a few have loosened up (more on this later).  
Initially, after reforming, all were trimmed to an overall length of 2.120”, 0.005”
shorter than the 2.125” overall all chamber length from the face of the breech
block to the start of the chamber-to-throat transition step.  If your cases are
stretching significantly or splitting prematurely you may be interested in reading
the article
Case Stretching & Separating in BPC Rifles.  

After firing, each case has been cleaned using ceramic media in a Thumler’s
tumbler and the necks annealed.  Although I “thumb-seat” bullets with minimal
tension it’s my opinion that annealing after each firing results in increased
accuracy due to uniform neck tension and also extends the life of the case by
delaying neck splitting.  To make the annealing process fast and simple I
purchased a Vertex brand Bench Source semi-automatic annealer.
Earlier I mentioned the primer pockets in several cases were looser than
normal.  Using a 0.210” pin gauge all 200 cases were measured and 28 had
pockets that had loosened up a bit although they all still held the primers in
place.  Rather than tossing the brass due to too loose pockets, the life can be
extended by flaring the pockets using a simple technique covered in the
following You Tube video:
https://www.youtube.com/watch?
v=1ST25CUpqhY&app=desktop.  After purchasing the two pin gauges and
5/8” chrome ball bearing on Amazon, I used the technique on the 28 cases and
it works great – how long the pockets will stay tight remains to be seen.  By the
way, filing the bases flat afterwards was not required with my brass.

Wishing you great shooting,
Wayne
Prior to reloading, since the Browning has a generous chamber neck diameter,
the case necks are resized using a neck resizing die and then expanded to the
correct size for thumb seating the specific bullet diameter being used.  The
necks are also flared slightly to ensure a tight fit in the chamber to center the
rear of the bullet and help in preventing hot gases blowing back along the case
(“blow by”).

As reported in a previous article discussing my test results of various brass
cleaning techniques (
Case Cleaning - Ultrasonic vs Tumbler with Ceramic
Media & Stainless Steel Pins), some case lip peening has been noted as a result
of the cleaning process.  When the collective amount of peening becomes an
issue (bullets hard to thumb seat), it’s removed using a mandrel inserted in the
neck resizing die as the necks are resized.  I.e., the peened lips are flattened out
rather than by removing any brass.  Here’s a link to an article on the process I
posted some time ago:
Removing Case Peened Lip Edge.  By the way, I
experience peening more so than some others since I anneal after each firing.

During the many reloading sessions the brass length has been spot checked to
ensure the lengths were within the maximum limit of 2.125”.  Some shooters
report their cases have shortened over time, but that has not been my
experience.  I just measured all 200 cases for the first time since they were
initially reformed and trimmed, and found an average length of 2.123”, some a
little more and some a little less.  I also found the case lengths were not uniform
around the perimeter of the mouth or lip.  I.e., the length could vary by +/-
0.002” to 0.003” depending on the location of the measurement.  So I decided
to trim all 200 back to a uniform 2.120” using a Hornady Camlock Case
Trimmer as displayed in the following photo.  With fingers crossed, maybe I’ll
get another 38 loading per case before they start to split.