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REPLACING BROWNING/WINCHESTER BPCR
FRONT SIGHT SPIRIT LEVEL VIAL
By Wayne McLerran
Updated: 2/4/16

The following is an updated set of instructions from my book titled,
Browning Model 1885 Black Powder Cartridge Rifle.

Cleaning & preparing sight for new vial installation:
The spirit level tube end caps are glued on with a cyanoacrylate ester
instant adhesive called 380 Black Max, manufactured by Loctite
Corporation.  Using a jeweler’s screwdriver or similar tool, gently pry off
both caps.  I’ve found a good stout pocketknife blade is the ideal tool.  
Preferably one you’re not real proud of in case the tip is broken or a
notch is broken out of the blade during the process.  Place the tip of the
blade flat against the rifle barrel with the sharp end of the blade
inserted in the small gap between the cap and vial housing.  While
keeping the blade flat, use it as a lever arm to pop the cap off.  Be sure
to catch the cap as it pops free.  To protect the rifle barrel finish from
damage it may be a good idea to tape the barrel where the knife or tool
will contact it.  Another method is to insert the sharp end of a knife
blade at an angle in the seam between the cap and vial housing then
lightly tap on the rear of the blade with a hammer.

Once the end caps are removed, with luck the broken vial can be pushed
out using a wooden dowel or similar tool.  But in most cases the end cap
adhesive has wicked between the vial and housing or the remaining dried
residue from the vial liquid has “cemented” it into place.  The adhesive
will have to be carefully chipped away and the remaining glass further
broken and picked out.

Once all the glass is removed, clean out the remaining residue or the new
vial will not slide in.  Although not ideal, Methyl ethyl ketone (M.E.K) is
the best solvent I’ve found to remove the adhesive.  Methylene chloride
(Dichloremethane or DCM), acetone or fingernail polish remover
containing acetone will work as a marginally effective “debonding agent”
to slowly dissolve the adhesive, although it may take some time and a lot
of scrubbing.  If the sight has been removed from the rifle and you’re not
in a hurry, soak the sight for twenty-four hours or more.  M.E.K or
acetone may not completely dissolve the adhesive, but it should soften it
enough for easy removal of the remaining residue and glass.  A Q-tip
swab is perfect for this.  While attending a silhouette match the only
recourse may be just scraping it out of the housing with your ever handy
pocket knife.  If a 9/32” or letter “K” drill bit is handy, use it by hand to
clean out the housing.  If the drill will slide through than all the gunk has
been removed.  If the housing has been damaged the drill can be used to
reform & straighten the housing.

Installing an original-type glass replacement vial:
If you’re replacing the vial with one of the original glass ones that I sell,
be aware that the diameter of the vials may vary by as much as 0.005”.  
In other words, the diameter may be somewhat larger or smaller or the
curvature may be slightly different even if the vial came from the same
manufacturing batch.  Therefore, a replacement may be too loose or
impossible to insert without slight modifications to the inside diameter
(ID) of the spirit level tube housing.  If it will not slide into a clean
housing, use some sand paper wrapped around an appropriate diameter
dowel to slightly enlarge the ID.  If it slides in loosely, the end cap
adhesive should lock the vial in place once it’s cured.  Also note that one
end of the glass vial has a lead plug sealing the fill-hole.  To avoid
damaging the seal, first insert this end in the vial housing.  And due to
the curvature the vial is sensitive to orientation.  Ensure the high center
portion of the curvature is oriented up.

As noted, some vials may slide in easily.  For those that do not, place a
piece of leather, thick cloth or similar material over the end of the vial
to protect your thumb in case the vial breaks.  Push the vial in as far as
possible.  Then use the wooden dowel to force the vial in slow and easy
until it’s centered in the housing.  A good rule of thumb is to end up with
a 1/16” gap between the bottom ends of the two black centering lines
on the vial and the bottom edge of the housing window.
NOTE – If the sight has been removed from the barrel, I highly
recommend reinstalling it prior to replacing the glass vial to prevent
shattering the vial during sight installation.

Installing an acrylic replacement vial:
The acrylic vials I sell are not sensitive to orientation, do not have a lead
seal to be concerned about and are not likely to be damaged during sight
removal and installation.  Assuming the vial housing is sufficiently clean,
slide in and center the vial.  The adhesive used to hold the housing end
caps will hold the vial in place once it’s cured.

Replacing spirit level housing end caps:
When the caps were originally installed, excess adhesive between the
inside of the cap and the end of the spirit level vial ensured the vial did
not rotate.  But the adhesive was too hard once it set up, resulting in the
loss of numerous caps due to thermal expansion differences between the
adhesive, metal tube and cap, no doubt made worse by the jarring
vibrations resulting from firing the rifle or removing and reinstalling the
sight.  If you’re fortunate to have the caps, prior to reinstallation,
remove the old adhesive from the inside surface by rubbing the cap over
some medium or fine sand paper to allow some room for the new
adhesive.  Apply a small amount of appropriate adhesive on the ends of
the vial and the inside surface of the caps and push the caps in until
firmly seated.  Tape or wrap a rubber band around the caps to hold them
in place until the adhesive cures.  I used whatever adhesive was handy.  
Goop brand all-purpose adhesive and sealant works fine as might other
types of adhesives or RTV sealants.  Using epoxy or super glues may make
it impossible to remove the caps if a replacement glass vial is ever
broken or requires refilling.
NOTE - replacement end caps are no longer available from Browning,
AMT (the original manufacturer) or any supplier so you’ll have to
improvise if yours are missing or lost.  One method is to fill the ends with
black RTV adhesive.

While attending a silhouette match, the caps on some sights can be left
off until later, assuming friction adequately holds the vial in place.  On
other sights, sealant may be necessary to keep the vial from moving.  It
depends on the shape and dimensional variances of the vial and housing.  
Prior to inserting the vial, squeezing the housing slightly out of round will
help to keep the vial from rotating once it’s forced in.  I’m aware of one
shooter that installed an acrylic replacement vial during a match.  He
jammed (wedged) the sharpened ends of a couple of tooth picks between
the ends of the vial and the housing to hold it in place until returning
home.

Wishing you great shooting,
Wayne