Drill, Tap & Install Receiver Sights
By J. Marshall Stanton
A decade or so ago, virtually every rifle and carbine manufactured in this country sported a set of factory drilled and tapped holes for mounting a receiver sight. Back before optics on rifles were either reliable, affordable or practical, a receiver sight was king over sporting rifles for true riflemen and hunters of the day.
Time has passed, and with it the days of factory drilled rifles for mounting receiver sights. Scopes rule the roost of modern rifles and riflemen, and gone is the excellent selection of well made receiver sights for many of todayís rifles.
Sadly, even the classic lever-action rifles and carbines that are making such a comeback in popularity these days arrive from the factory without proper mounting holes for traditional receiver sights. Yes, the Winchester 94ís and Marlin 336ís, 1894ís and 1895ís are drilled and tapped for top scope mounting, but not for the traditional side-mounted receiver sights. Both Williams and Lyman have designed receiver sights that utilize the scope mounting holes, but those sights sit up a fair bit higher than those receiver sights many of us have learned to love.
Also, beyond the American lever-gun standbys are the imported clones of the
1892 and others that benefit greatly from a good, old-fashioned receiver sight screwed to their side. Additionally, these guns with their top-ejection of spent casings preclude the practical mounting of a scope, and for those of us with aging eyes, a peep sight is as good as it gets.
Gunsmiths today make a fine addition to their monthly receipts doing tap-and-drill jobs on many of these rifles and carbines for the purposes of mounting a good receiver sight. Their services are both needed and appreciated, but for many of us, thereís the satisfaction of doing things ourselves and saving a few sheckles along the way, both in the work performed and by avoiding the absurd charges incurred in shipping a gun anywhere these days.
It is to this self-sufficient readership that this article is presented. This is a brief whirlwind trip through a simple drill and tap job on a Rossi M92 for mounting a Williams 94/36 5D receiver sight. The process and procedures are the same for many makes and models of rifles, and it doesnít matter whether you are mounting a new Williams or Lyman sight, or perhaps an older sight from these manufacturers, or maybe an old Redfield peep sight; the principles are the same, it isnít expensive, and it isnít rocket science.
The first step is to MAKE CERTAIN THE FIREARM IS NOT LOADED, then gather all your necessary tools and materials together and make sure that you have a place to work. In this case we are mounting the Williams 94/36 5D sight to a Rossi M92 rifle. The necessary tools for this project are as follows:
- #31 size wire gauge drill bit
- #26 size wire gauge drill bit
- 6-48 taper tap
- Tap Wrench
- Tap-Magic Cutting Oil
- Drill Press
- Center Punch
After unpacking the sight to be mounted, disassemble the unit and put the parts into a small parts pan or dish to prevent loss. Then, taking the sight base only, align on the side of rifleís receiver in proper position for clearance of the action and correctly squared to the top of the receiver. Once properly positioned, use a sharp scribe to mark the location of the hole centrally located in the sight base under where the sight elevator slides up and down through the dovetailed slot in the base. Once the hole location is marked using the scribe, remove the sight base from the receiver, and carefully center-punch the marked location for the first mounting hole.
Using the #31 size wire gauge drill bit in a sturdy drill press (bench top drill presses work just fine) with a padded surface for the rifle to rest upon drill the first hole in the receiver after first double-checking that everything is square to the axis of the arbor on the drill press, and that the drill bit wonít contact internal working parts. In the case of this, simply open the action (on a Rossi M92) and drop the locking lugs out of the way of the drilling operation; however, on some actions disassembly of the action mechanism may be necessary prior to this step.
Once drilling is accomplished for the first mounting hole, it must be tapped for threading in the first mounting screw holding the sight base. Affix a 6-48 taper-tap into a tap wrench, then lube the tap with a generous coating of cutting fluid such as Tap-Magic or another good quality cutting oil. This lubrication of the tap cannot be over-emphasized, as these are very finely machined tools and easily broken, and, trust me, it only takes one broken tap stuck in a very fine rifleís receiver to really spoil your day! After lubing the tap, make certain that as you insert the taper-tap into the drilled hole that it is perfectly square with the receiver, and aligned with the hole, then carefully turn the tap wrench clockwise while exerting slight downward pressure while cutting the threads into the freshly drilled hole. Run the tap all the way down to the point that it freely turns without much effort, adding a drop or two of cutting oil every couple of turns on the tap wrench during the process. Then, reverse the wrench and spin the tap out of the hole counter-clockwise; while the tap is backing out of the hole, it will clean and dress the threads as well.
Using a paper towel, wipe any drill or tap cuttings free from the receiver, both outside and inside, then mount the receiver sight base to the rifle using the short screw included with the sight, insert it through the centrally located hole in the sight base, and tighten the screw just slightly snug in order to hold the base firmly in place, properly aligned as when originally laid out on the rifle.
With the sight base firmly affixed to the rifle receiver, now remove the #31 size wire gauge drill bit from the drill press and replace with the #26 size wire gauge drill bit. Then, with rifle resting on the padded drill press table, align the receiver carefully so that the drill in the press is aligned with the second screw mounting hole in the sight base. This drill is the exact size as the hole drilled in the receiver sight base, and so the sight acts as a guide to precisely position the drill bit for the second mounting hole. Turn on the drill, and carefully run the #26 drill bit down through the mounting screw hole in the sight base until it contacts the receiver. DO NOT DRILL THE RECEIVER WITH THIS BIT! The purpose is to slightly pilot-drill the hole, centering and marking the location to be drilled with the #31 drill, as seen in the accompanying photograph. By using the method described in this article, you will never run the risk of drilling holes that are either misaligned or have improper screw spacing. Follow these directions and these problems will not plague you.
Now, remove the screw holding the sight base onto the side of the receiver and the sight base. Remove the #26 size wire gauge drill bit from the drill press and replace with a #31 drill bit, then drill the receiver where it is marked and pilot drilled.
Once again apply a liberal coating of cutting oil to the 6-48 tap, and carefully tap the second mounting hole, using the same technique as with the first hole. Make absolutely certain that the tap is perpendicular to the receiver surface and true with the drilled hole before tapping. When finished, clear the action of metal debris remaining after the drilling and tapping process.
Congratulations! You have just completed drilling and tapping your rifle to accept a traditional style receiver sight! Now the time has come to install the sight base on the rifle. I like to use a coat of either paste floor wax or automotive car wax on the receiver prior to installing the sight base. This virtually prevents the possibility of rust-causing moisture on the receiver under the sight base. Then, using either clear fingernail polish (my personal choice) or Loc-Tite on the sight base mounting screws, install the base, being sure to torque the screws down snugly.
When installing the sight elevator and aperture assembly, setting the sight so it is roughly adjusted to point of aim is relatively easy, provided the original rear open sight is left in place up until this point. If so, simply sight down the rifle, looking through the newly installed peep sight, and move the rear aperture whichever direction is necessary to align with the existing sights when they are properly aligned on a distant target. Once you can look through the aperture and see the rear sight properly aligned with the front sight and centered in the rear aperture, lock down the adjusting screws on the receiver sight. Now, remove the existing rear sight from the rifle. Fill the remaining screw holes with plug screws, or, if a dovetail sight, fill the empty dovetail slot with a slot blank. Do final sight adjustments at the range after shooting a group on target, and move the rear aperture accordingly to bring point of aim into alignment with point of impact.
See, the job really wasnít that difficult, and now you have the tools and know-how to do it again next time.