Replacing Browning/Winchester BPCR Front Sight Spirit Level Vial

The original Browning glass vials had to be orientated correctly when installed. They have a lead seal that holds the liquid in and can come loose, and they are rather easily broken. Also the dimensions of glass vials, both length and diameter, vary more than acrylic vials. AMT, the manufacturer of the sights for Browning purchased thousands of glass vials from a supplier and was forced to “cherry pick” vials that would slide into the vial housing. When AMT discontinued making sights, most of their remaining inventory of vials were slightly too large to fit. In contrast the acrylic vials I sell are not sensitive to orientation, do not have a lead seal that can come loose, and are not likely to be damaged during use, sight removal and installation. Plus they are easy to install once the housing is sufficiently clean. The one negative is the yellow/green acrylic liquid is not as “brilliant” as the liquid in the original glass vials.

Cleaning & preparing sight for new vial installation

The spirit level tube end caps are glued in place 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. Another, likely easier method is to insert the sharp end of a knife blade or the edge of a common flat tip screwdriver at an angle in the seam between the cap and vial housing then lightly tap 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 bit shank can be used as a mandrel to reform & straighten the housing. Insert it in the housing as you tap on the outside with a small hammer to reshape the housing.

Installing an acrylic replacement vial

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 in the unlikely event the acrylic vial needs to be replaced.

NOTE - replacement end caps are no longer available from Browning, AMT (the original manufacturer) or any other supplier, so I made some for sale using my lathe.

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