The Hobby Gunsmith

Project -

We Reduce the height of a Marbles Tang Sight.

As regular readers of The Hobby Gunsmith are aware, we obtained an Lightning Rifle from American Western Arms.  We shot the gun for over a year using the factory sights.  The front sight was upgraded by AWA and is very nice with a brass insert.  The rear sight is the upgraded semi-buckhorn sight that is made out of stamped steel and was bent slightly when it was shipped back to me from AWA.

   Last year we showed how to install both the Marbles and Lyman front sights on a pair of Winchesters.  We found the tang sight to be very helpful in keeping our old and tired eyes in the right place as we worked the action of the Winchesters.  We felt it might be an advantage to also use a tang sight on the Lightning.

   We purchased a Marbles Tang Sight from Midway USA that was listed as being for a Colt Lightning.  We installed the sight be removing the stock retaining bolt from the tang, setting the tang sight into place, and holding it down by reinstalling the stock retaining bolt to hold the tang sight in place.

The tang sight as received from Midway USA.

   With the sight in place, it can be sighted in by adjusting the tang sight to provide the proper sight picture with the original sights.  Our lightning was sighted in with the front bead at the very bottom of the semi-buckhorn rear sight, but the tang sight would not adjust down low enough to give us that sight picture.  The tang sight would not come down low enough.

   In order to allow us to use the new tang sight in competition, we will have to modify the Marbles tang sight and shorten it enough to allow it to be adjusted to point of aim for several kinds of loads that we might use in the future.

Here is the sight picture of the sight showing the front post way too high.  Yes, we have since cleaned the bench and moved the television.

   We began our modification to the tang sight by sighting through the tang sight and then lowering our eyes on the outside of the sight to determine how much we need to shorten the sight to allow the correct elevation.   We used a dial caliper to measure down from the center of the rear sight aperture to the point below the aperture where we can get the correct elevation.  We added just a little more for adjustment of different loads and decided to shorten the sight by a quarter of an inch.

   We removed the sight from the gun and began dismantling it.  We placed the sight on a rag to catch any parts that fall from the sight.  We began by using an Allen wrench to remove the setscrew in the knurled base of the sight where elevation is adjusted.

With the Allen screw removed, the balls are visible through the threaded hole.

   The Marbles tang sight elevation adjustment is made of a vertical tube with slots in the front and rear.  The vertical piece with the eyepiece is threaded with a pin that slides in the slots of the lower tube.  The knurled adjustment screw is threaded on the inside and is retained by a series of ball bearings that are under the Allen setscrew.  The detents are provided by a series of dimples in the base of the adjustment screw and a small ball that sits atop a recessed spring in the base of the sight.

This photo shows the pin that slides in the track and keeps the eyepiece aligned with the barrel.

   To shorten the sight, we must begin by removing the little balls that hold everything together.  We carefully removed the little setscrew and started turning the elevation adjustment while pointing the screw hole down so the little balls can roll out of the bearing race.  With all of the balls removed, the elevation adjustment will slide off the top of the base tube.

This photo illustrates the relationship between the alignment pin and the threads.  This must be maintained after cutting the shaft.

   We next removed the alignment pin by drifting it out over a block with holes in it.  Once the alignment pin has been removed, the knurled adjustment piece can be unscrewed and the upper portion of the sight may be removed.  The pin was drifted through a flat section of the upper sight that must be reproduced after the upper threaded section of the sight is shortened.

 

We translate the amount we estimated the sight was too high and transfer that to the threaded portion that must be cut.

   We used a cutoff wheel on a Dremel tool to remove about a quarter of an inch from the lower threaded end of the upper portion of the sight.  We then used the cutoff wheel of the Dremel to machine a new flat section in the threaded section of the upper sight.  The flat section must be perfectly parallel to the sight ring since the position of the flat portion of the threaded area determines the alignment of the sight.

 

 

   With the new flat area machined in the end of the threaded portion of the top section of the sight, we clamped it in a cross-sliding vise so we could use the drill press to bore a new hole for the alignment pin.  With the new hole bored in the new flat spot, we are ready to reassemble the Marbles tang sight.

Here we drill the new hole for the alignment pin.

   Reassembly begins by threading the upper section of the sight into the knurled adjusting piece.  We pressed the alignment pin into the new hole and then pushed the threaded upper sight and alignment pin into the slotted base and pushed it down and almost into place.

   The last two parts of the assembly are a bit tricky.  First, we glued one of the little balls onto the recessed spring with a little bit of gun grease.  This will hold it in place while we assemble the rest of the balls.  Next we pressed down on the knurled adjustment to put pressure on the recessed spring while we insert the balls down through the hole for the setscrew.  We found it helpful to insert a ball into the bottom of the hole and then turn the elevation adjustment while pushing down against the detent spring.  We inserted balls and turned the adjustment until we were able to reinstall all of the balls.

Don't forget to "glue" the little ball on the spring with a little grease to keep it in place while assembling the sight.

   With the balls reinstalled in the bearing race, the setscrew should be reinstalled to prevent any of the balls from escaping.  We then reinstalled the sight on the tang of the Lightning rifle and adjusted the elevation and windage screws until we can look through the ring and see the sight picture in the factory sights that are the same as we held when we used the factory sights.  At this point, we could remove the original semi-buckhorn rear sight, but we elected to keep it in place.

Here is the completed and lowered sight.  We still need to anchor the front with a screw.

 

We took the gun with its new tang sight to a Cowboy Action Match in Manteca, CA to try it out.  We used the AWA Lightning along with the new Ruger Blackhawk that is rebuilt in this issue to shoot a clean match with an above average placement in the standings.