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.40-65 BPCR
By Wayne McLerran
Posted 11/26/18

This article is about a couple of bullets I designed for use in the Browning 1885
High Wall .40-65 BPCR.  Both of the single-cavity moulds are available from
Buffalo Arms Co. (BACO).  The JIM410410M3 mould/bullet, hereon referred to
as the M3 bullet, was previously described in detail in the following article:
Bullet Design & Loading Considerations for the Browning .40-65 BPCR.  The
one distinguishing feature between the M3 bullet and the newer design M1 bullet
discussed below is the diameter of the nose driving band.  The M3 nose driving
band is the same diameter as the nose whereas the M1 nose driving band is
0.010” larger than the nose diameter.  So at this point you’re likely wondering
why the two different designs?

The M3 bullet was configured to load with a good bit of powder, significantly
more than the typical 55 to 62 grains or so used by many .40-65 silhouette
shooters.  Since the Browning has an extended throat with approximately 0.190”
of effective freebore, the bullet, sans nose driving band, must be seated well out
of the case in order to contact the leade.  Therefore, unless it’s loaded short (off
the leade) or additional wad material is used to fill the case capacity, around
65grs of Swiss 1.5Fg will be required to fill a fire-formed Remington case when
using a 0.060” wad and only 0.020” compression, resulting in an overall
cartridge length of around 3.2”.  Using the same wad thickness and powder
compression with Winchester or Starline cases will require slightly more or less
powder respectively.  By the way, I have shot the M3 bullet with up to 68 grs of
Swiss 1.5Fg and 0.120” of compression with good accuracy.

Desiring a milder load with low powder compression, I requested that BACO
make one modification to the M3 mould, increase the diameter of the 0.100” long
nose driving band from 0.400” to 0.410”; the same diameter as the other driving
bands.  Increasing the nose band diameter results in seating the bullet back into
the case approximately 0.150”, reducing the powder charge by 5 to 6 grains with
a 0.060” wad and light compression, which Swiss prefers based on my testing
and as reported by others.  BACO agreed to make the change and decided to add
the mould to their listing as JIM410410M1.  By the way, I had a good laugh
when I read their description of the mould, which included the comment
“Designed by Wayne McLerran, he made us make this mould for him”.
With the two bullets pictured side-by-side, the obvious difference is the increase
in diameter of the 1st driving band of the M1 Bullet.  And the M1 lube grooves
appear to be slightly longer which they are but not a significant amount.  The
larger nose band adds slightly to the weight, which is reduced to some extent by
the wider grooves, resulting in 410.3 grs versus 410.0 grs for the M3 bullet
when cast with 20:1 alloy.  Using 16:1 alloy reduces the weight of both versions
by approximately 2.5 grains.  I recommend 16:1 alloy with “Money Bullet”
designs to minimize the possibility of nose slump.  Although both are “nose
ridding” bullets, meaning the nose or most of it will be in the bore, due to the
tapered design a substantial portion of the nose is not supported by the bore.  
Therefore if the alloy is too soft the nose may slump, resulting in an unbalance
and therefore an unstable bullet, especially at longer distances.  The slightly
larger nose driving band also decreases the ballistic coefficient slightly but not
enough to be a concern.

I’ve found the M1 bullet shots best in my Browning with 59 to 62 grs of Swiss
1.5F, resulting in approximately 0.020” to 0.090”of compression with a 0.060”
wad.  Due to the factory chamber and throat design I do recommend using a
0.410” diameter bullet in the Browning.  As to which bullet, the M3 or M1, is
more accurate, it will depend on your rifle and load configuration.

Wishing you great shooting,