Note: There are many things that we take for granted, gloss over, assume we know, or do not want to admit we may be a bit behind the curve on.
The Devil is in the details and when lives are at stake, leave nothing to chance. (Yes, I borrowed that from an H&K T-shirt I had in the early 90s.) In this and forthcoming issues of this column in TW, we will deal with the Devil’s Details, pivotal pieces of tradecraft that can make the difference between a mission accomplished or a mission failed. We will keep these details germane and useful, because chance favors the prepared.
Recommended Specialty Tools and Why:
Tools Needed: Lap bar, lapping compound, level and a torque wrench.
Why These Tools? A level needed for use on the rifle and the scope. A standard level will work, but the one like CTK Precision offers will certainly make the job easier.
A lap bar is a cylinder used to align the ring bases and polish them into alignment with each other and to the scope. The lapping compound is a gritty paste that acts like liquid abrasive and works with the lap bar to polish the rings until they are parallel to each other. The torque wrench will enable you to tighten the clamping bolts fully and uniformly without fear of damaging the hardware or the scope.
Identify the torque specs for your make of hardware for the mount base and the ring mount bolts. As an example, the NightForce rings that I am using specify a maximum of 15 inch/pounds for the rings and 68 inch/pounds for the mount base nuts. Next, set the lower halves of the mounting rings on the scope base and finger-tighten them. Get into your preferred shooting position and obtain an appropriate cheek weld. Place the scope on the ring halves to determine the best location of the rings and scope placement to optimize eye relief. To avoid scuffing the finish of the scope, pick the scope up and move it back and forth rather than slide it. Once you find the optimal position, put a piece of masking tape on the scope and make an alignment mark to identify where it needs to be located, and then remove the scope.
Secure the rifle in a padded rifle vise. Place the lap bar in the bottom half of the rings. Loosely install the top halves of the rings. Loosen the ring base mounting nuts and press down on the lap slightly while wiggling the rings and align them to each other and the base. With the lap installed, tighten the top halves of the rings with a moderate tension. Hold the lap and tighten the ring base nuts to the proper torque specification with two releases or clicks of the torque wrench. For the more precise tension setting required for the scope rings, I prefer to use a preset, single-torque-setting wrench.
Unscrew the top ring halves and remove the lap. Once you start lapping, it is imperative that you replace the ring tops on the same ring base in the same direction every time. Mark them so they don’t get reversed! As the lapping process progresses, the amount of blue finish on the base of the bottom rings is used as a progress indicator. Use a felt-tip marker as an indicator when lapping in rings that have been previously lapped.
Rub lapping compound around the lap bar approximately two inches on each side of the center lap bar handle. Place the lap bar with compound in the scope ring bottoms and screw in the tops of the rings. For the first lap session, tighten the top rings so the lap is able to move, but is firm. How tight the tops need to be tightened is a matter of feel and will take some experimentation. If the tops are too loose, the lapping will be ineffective: if they are too tight you will not be able to move the lap.
Slide the lap bar back and forth rotating it 90 degrees with each stroke for 30 strokes. Remove the lap, clean the compound off and inspect the finish at the bottom of the bases. The parts of the rings where the finish is removed are the only parts that have been made parallel. If less than 80% of the finish or marker ink has been removed from the bottom half of the rings, add fresh compound to the lap and lap again with the top rings tightened slightly more than you did the previous time.
Tighten the top half rings evenly to keep everything parallel, preventing binding. Repeat as necessary until 80% of the finish or marker ink is removed from the bottom of the rings. The top halves will lap-in as you lap the bottom halves but usually not as much as the bottoms. The bottom ring halves are the most critical to scope alignment and secure mounting. Do not lap until the ring halves are fully tightened against each other, or they will have little holding power.
The number of times that you have to repeat the process will be determined by how far off parallel your mounts are, the durability of the finish, and hardness of the metal the rings are made from. My NightForce mounts are quite stout and took several lapping sessions.
Leveling the Scope
Thoroughly remove the lapping compound from the rings and screws. Insure that the rings are clean. Level the rifle in the vise using a level seated perpendicular across the ring base. Remove the scope turret covers—if so equipped—and set the scope at the previously determined location.
Place a level atop the vertical turret. If your scope is not level to your rifle, turret adjustments will be off kilter, throwing off your point of impact. Attach the top halves of the rings on the bolts making sure the gap between the ring halves remain even on each side—this can be checked by looking at the gap between the top and bottom rings from the sides. All eight ring-bolts should be tightened to the same slight tension level.
The tightening should be done in an “X” pattern (see illustration.) Tighten the screws equally. It is important to tighten each screw a little at a time to keep the tension even—1/4 rotation at a time is good to start with. As the screws get tighter, switch to a torque wrench and use 1/8th turns. The job is complete when the wrench has released twice at the proper specification on each bolt.
Words of caution: The rings are lapped to that rail position only, if you move the ring bases to another rifle or even to another location they need re-lapping. In that case, color the bottom of the rings with a felt-tip marker to use as your indicator.
Gunsmithing Tools: Buy Them Once, Buy Them Right!
Having bought my share of power tools, I learned a long time ago that buying cheap is a mistake. Most often, they don’t work well or they don’t last. The same can be said for gunsmithing tools.
Scope Ring Alignment Lap
The only “true” specialty tool needed for lapping is a scope ring alignment lap. In addition to lapping the rings to make them even and parallel, the lap is used to align the rings before mounting to the base. Made of solid metal, Brownell’s makes laps made of solid metal.
Torque Tool Benefits
Scope mounting requires a torque wrench. It will insure that your scope doesn’t get damaged by over tightening the rings. Among the most precise are the torque handles by Seekonk Precision Tools available in seven preset torque settings. They’re useful for scope mounting and improving accuracy by setting all vital screws in your rifle to the same pressure.
Wheeler Engineering’s FAT (Firearm Accurizing Torque) Torque Wrench Screwdriver is a versatile alternative to single-setting torque wrenches. Cheaper than buying multiple wrenches, the FAT offers settings over a 10-60 inch/pounds range. This one driver can tighten the ring screws at one setting and the base nuts at another, as well as just about any other firearm screw. Included is a square drive adapter and nine bits including: Leupold/Buehler windage bit; T10, T15 and T20 Torx bits; 3/32″ and 5/32″ Allen bits; and #10, #11, and #12 deluxe hollow-ground flat blade bits.
Gunsmithing Screwdriver Sets
Wheeler Engineering offers the solution to mating the right bit to the job with its multi-piece professional gunsmithing screwdriver sets. Available in 17-, 72-, and 89-piece sets, all bits are made from S2 tool steel and hardened to 56-58 Rockwell “C” to insure durability. The Wheel screwdriver sets can also be used with the FAT Torque Wrench Screwdriver.
Need A Third Hand? Get A Quality Gun Vise
The CTK Precision P3 Ultimate Gun Vise’s versatile design will hold any style stock configuration and can be used with rifle uppers, barreled receivers, or bare barrels. The P3 holds the parts with minimal clamping pressure with a solvent-safe, closed-cell PVC foam padding.
Note: There are many things that we take for granted, gloss over, assume we…
by patrickdurkin / Feb 21, 2008