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MY BPCR BORE LEADING SAGA
By Wayne McLerran
Posted 10/8/19

When I started competing in local BPCR silhouette in mid-2012 I used a blow
tube but struggled with bore fouling issues, most likely due to inconsistent or
insufficient blowing technique.  Attempting to deal with the temperature changes
from match-to-match in Central Texas was a struggle, especially during the
summer.  Based on recommendations from several experienced shooters at the
time I switched to bore wiping, first starting with RV antifreeze solution, then
“moosemilk” (Murphy Oil Soap and water), and eventually to a solution of Napa
brand water-soluble oil and water.  The water removes the fouling and the
soluble oil lubricates the bore for the next shot.

Things were going well and after 3 years of competitive shooting I eventually
moved up to AAA classification.  Another year passes while attending 15
matches with mostly AAA scores.  Feeling pretty good about my shooting
ability I signed up for the annual Texas State Match.  After the first day of the 2-
day 40-shot-per-day match I was in 2nd place with a 29 and figured I had a real
chance at winning the scope category.  The next day was when disaster struck
and bore leading reared its ugly head.  I couldn’t hit anything consistently
including the pigs and ended up with a score of 19 and a total of 48 for the
match, which placed me in the middle of the pack.  To say I was disappointed
was an understatement.

After returning home and using a bore scope the problem was evident – lots and
lots of leading which started a couple of inches in front of the chamber to about
¾ of the way down the bore.  When cleaning the bore with very tight patches
soaked in turpentine the patches came out with long strips of lead.  I was using
16:1 alloy 398gr bullets (BACO JIM409400M5) lubed with White Lightning
over 69grs of 1.5Fg Swiss and a 0.060” fiber wad.  The load resulted in a
velocity of 1330fps.  Due to the combination of the extended freebore in the
throat and the tapered bullet driving bands, the compression was only 0.010”
with the driving band contacting the leade.  This is a relatively “hot” load but
after a year of shooting the same loads this was the first indication of leading.  
Scratching my head as to what was going on I spent some time attempting to
figure out what changed while researching the possible causes of bore leading.

I considered the most common causes including the bullet diameter being too
small, allowing hot gasses to blow by, i.e. gas cutting prior to the bullet bumping
up (obturating) to fill the chamber and throat.  Another is the alloy could be too
hard preventing the bullet from obturating sufficiently or quickly enough.  Other
possibilities include inadequate lube or the cartridge overall length was too short
(bullet seated too deep) allowing blow by.  But none of the above made sense
when considering past successful shooting results with the same bullet cast from
the same alloy, with the same lube and reloaded the same.  And the cartridge is
certainly not too short since the 1st driving contacted the leade.  Plus, I wipe
between shots which would compensate to some extent for inadequate lube.

Several more matches followed the Texas State Match including a trip to the
NRA Whittington Center BPCR Nationals with mediocre to poor scores as I
struggled to figure out the cause of the leading.  I even changed bullets and
reduced the velocity but the leading persisted.  Nothing was obvious until I
overheard a discussion between two shooters.  One guy mentioned that if the
wiping patches left too much solution in the bore, leading would result.  The
comment struck a chord.  Prior to the 2nd day of the Texas State Match, after
soaking the wiping patches in a solution of soluble oil and water, I’d been
squeezing them out until most of the liquid was removed, leaving the patches
lightly damp.  When preparing for the 2nd day of the match I’d decided to leave
the patches wetter to better clean and lube the bore, and continued to use them in
the same condition for subsequent matches.

They were wet enough that some of the solution would leak into the action when
inserting the patch into the chamber.  Following the overheard conversation the
patches were squeezed out good but left damp for the next match.  That did the
trick; there were no signs of leading with the exception of a few tiny flakes.  
Since then I’ve shot in many matches with the same outcome.  Who would have
thought…?  Too dry of a wiping patch can result in poor accuracy due to burnt
powder and lube fouling remaining in the bore.  Apparently too wet will have
similar results due to leading, another form of bore fouling.

By the way, after solving the leading problem, I’ve been experiencing vertical
stringing on the turkeys and rams.  During another discussion between match
relays a very experienced shooter mentioned that too much soluble oil in the
wiping solution can result in vertical stringing.  He recommended no more than a
7:1 (water to oil) mix.  I had recently increased the oil concentration from 10:1 to
a 5:1 mix, figuring the additional oil would do a better job of lubricating the bore
in the very hot Central Texas heat.  So now I have another variable to experiment
with and possible “fodder” for a future article.  Nothing comes easy in this sport,
inviting lots of experimenting, which is one reason I enjoy the challenge of
reloading as much as the shooting.

Wishing you great shooting,
Wayne