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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