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SADLAK Scope Mount: SADLAK's scope mount is an ideal way to add optics to M14/M1A rifles.

Optics are becoming increasingly more common on military rifles. While classic self-loading military rifles such as the M14/M1A were released a generation before this trend, SADLAK Industries (sadlak.com, 860/742-0227) has a ready solution.

Mike Sadlak started in the industry in 1989 as Sadlak Innovative Design, an engineering studio developing solutions for manufacturing and assembly companies. As his company grew, he sought out new opportunities and began looking into components for firearms. SADLAK Industries has two primary product lines, one in the AR market featuring their gas blocks and the other for M14/M1A rifles featuring their Premium Scope Mount.

Prior to SADLAK's design, Brook-field Precision Tool was the original designer and manufacturer of this type of mount. Commonly known as a three-point contact M14 scope mount, the Brookfield was an improvement over the original aluminum military mounts. When Brook-field ceased operations in the mid-1990s, Mike Sadlak offered his own design with a number of important improvements.

First was the increased length and addition of two outboard set screws to the clip guide key. The outboard setscrews wedge the key into the dovetail groove of the stripper clip guide for maximum surface contact and holding power. The key acts as an immobile stationary nut, which is more secure than the Brookfield design and offers a better anchoring point for the mount at the stripper clip guide area that is better able to withstand the recoil forces without loosening.

With the clip guide key securely wedged and locked into the dovetail groove, the elongated slotted hole allows more adjustability without sacrificing holding power and allows the screw to better mate up with the stationary nut. Rather then depend exclusively on a small #10 socket head cap screw for secure holding as with the Brookfield design, SADLAK's approach is more robust.

An added five-degree case deflection angle on the mount's underside allows spent cartridges to better clear. With a worn ejector, the spent case can be thrown vertically and hit the mount. SADLAK's additional clearance helps alleviate this.

Added semi-circle notches on either side of the mount allows the clip guide key to be tightened in the receiver groove while the mount is attached for more convenient installation. The increased screw size of the third contact point (from 1/4-28 to 5/16-24) contacts the top front of the receiver for greater contact surface with the receiver. Finally, only two hex wrenches are required to service the mount.

Receiver Assessment

Before installing on a given M14/M1 A, the receiver must be inspected due to a number variations in manufacture. SADLAK has a receiver groove inspection kit to help troubleshoot scope mounting problems due to an out-of-spec receiver groove. Especially if a shooter is experiencing windage or elevation problems, a receiver inspection will determine specific dimensions and confirm if the mount is correctly installed.

This inspection kit consists of a set of precision-ground pins used to inspect the receiver to determine if the left side groove is within normal specifications. The large pin measures 0.1563 and the small pin 0.1406.

The groove has tapered side walls and must be measured over a round pin to accurately determine the width. In addition to the inspection kit, you'll need an accurate measuring tool, such as a six-inch dial caliper (good) or a two-inch micrometer (best). A magnifying glass or eye loop is recommended.

The first step is to identify which of the two inspection pins best fits your receiver. Cut a strip of paper no wider than the width of the groove bottom and allowing for a tab for grasping. Secure a pin in place with rubber bands on top of the paper strip in the groove. If you can pull the paper strip out from under the secured pin, you'll know the pin is not in contact with the bottom of the groove and is the appropriate size.

With the correct pin chosen, there are four important dimensions when using this kit. Dim. 1 is the groove width, which is the same as the appropriate-sized and secured pin height above the left surface. Find this by measuring the receiver width and then subtracting that from the total thickness of the receiver width with the pin in the groove.

Dim. 2 is the groove depth and is found by measuring the depth of the groove with a dial caliper or depth micrometer using the probe function in the normal manner. Magnification helps here.

Dim. 3 is the groove bottom width and Dim. 4 is the groove top width. Both are taken with an inside caliper or micrometer. While these dimensions are difficult to measure precisely due to the small corner radius breaks, they aren't as critical as the first two dimensions and serve as an additional sizing reference when all are combined. Do your best to get the measurements to a theoretical sharp corner. Magnification is really helpful.

Start with the appropriate-sized pin. The pin should rest on the angled face inside the groove without touching the groove bottom or contacting the corners on the widest part of the groove--hence the paper strip test. The small pin works best when the groove depth (Dim. 2) is less than 0.055" or the groove top width (Dim. 4) is less than 0.135. For USGI specifications, Dim. 1 with the large pin measures 0.102-0.106 and the small pin measures 0.079-0.083. For Dim. 2, the same USGI spec will have a groove depth of 0.062-0.072. The SADLAK readily adapts to non-GI spec receivers and handles Dim. 2 measurements from 0.055- 0.075 without customization. With the measurements taken, we're ready to install.

Installation

Begin by removing the stripper clip guide from the receiver. Inspect for burrs on the angled surface and inside the dovetail groove, moving any with a stone. Note, careless removal of the stripper clip guide can crack the receiver. Remove the stripper clip guide by removing the receiver from stock.

From the inside of the receiver, insert a 3/32 diameter or slightly smaller pin punch and gently tap the spring pin out. While supporting the left side of the receiver below stripper guide with a block of wood, gently tap the stripper guide on the right side only. The stripper guide is removed from right to left.

Inspect that the tapped hole in the receiver has good clean threads by manually threading the hex screw into the hole. Don't use a wrench as damage to the receiver or screw may occur if threads in the receiver are dirty or damaged. If threads are good and clean, the screw will easily thread into it without binding. Use solvent, a small brush, and/or compressed air to get them that way. If required, chase the thread with a #12-32 UNEF (Extra-Fine) chase screw. A hand tap may be required if the threads are severely damaged. The chase screw, repair tap, and 3/32 Starrett Pin Punch are available from SADLAK. Note, SADLAK's chase screw uses a more fine pitch than the #12-32 UNF or UNC commonly found in hardware stores, though some large industrial tool supply companies might carry the item.

To install the mount, place it in the receiver groove on the left side. Slide the mount toward the barrel and then back to check surface contact. To help confirm contact, Permatex Prussian Blue high-spot marking paste can be used. The left side key on the mount should fit completely into the receiver groove. When pressed firmly against the receiver, no light should be visible between the mount and receiver. Full contact between the mount and the machined surface on the receiver's left side will help assure maximum reliability, help return to zero when the mount is removed, and prevent loosening due to recoil.

Insert the cam washer into elongated slot in left side of the mount at 9 o'clock. Install the hex screw after applying Loctite (SADLAK recommends 222MS for their mount) and inserting through the cam washer and into the receiver. Partially tighten the screw with a 3/8 box wrench about a 1/8-turn past hand tight. This creates full contact with the receiver while being able to slide towards the stripper clip guide angled face. The mount should not have contact with the receiver angled face and a small light gap should be visible.

Lightly tap the tab on the cam washer with a plastic mallet clockwise until the mount rides up the angled face while the hex screw remains moderately tight. Prepare the clip guide key by removing two small set screws in the clip guide key and apply Loctite. Re-install into the key until flush. Install the clip guide key by sliding into the dovetail slot in the receiver and visually align with the center-threaded hole in the key. Note, the key may require fitting due to variations in the dovetail dimensions. The key is made of soft steel to allow hand filing to obtain a tight slip fit, so file it to fit as needed.

After threading the screw into the clip guide key, partially tighten it, and lock the key into the dovetail slot. Tighten with an inch-pound torque wrench. The hex screw needs to be 60-65 in-lbs, the two set screws in the clip guide to 20, and the clip guide screw to 30-35. Screw down front post screw until contact is made with the top of the receiver after applying Loctite, tightening to a 1/2 turn past hand tight.

The scope mount installation is complete. SADLAK recommends re-torquing scope mount screws after the first 1,000 rounds.

Troubleshooting

Original USGIM14 specifications will fit great as the mount was designed for that but later military and civilian makes may have been machined differently Four problem areas are the left side horizontal groove (sometimes the groove is not cut deep enough), the stripper clip guide angled face (sometimes it is too far forward), the left side surface (sometimes it is not milled parallel to the barrel or is tapered), and the tapped hole (sometimes the location isn't correct from receiver front.) Older receivers tend to have a better track record. If your MIA receiver is made correctly on the left side, this mount will fit against it perfectly. The key on the inside of the mount is made smaller to fit inside the horizontal groove with only a small amount of play. Any visible light gap between the mating surfaces indicates a non-GI specification receiver.

Most fitting problems are due to the left side groove being machined too shallow. This causes the scope mount key to contact the groove, forcing the mount off the receiver and cocking the rail to the right with visible light showing. According to USGI receiver drawing #7790189, the 60-de-gree groove on the left side should be 0.070-0.078" wide at the bottom and 0.149-0.153" wide at the top as calculated from the gage point, which is 0.0312 below the left side surface.

The reason variation among receivers is that private manufacturers are not under a government contract, do not have to strictly adhere to the government-issued blueprint specifications, and are not inspected using government source inspectors and approved gauges. The mount can accommodate any of these "other spec" receivers and SADLAK can modify your mount as needed. Be sure to take measurements as stated above to get the modification done right.

by Bill Smith
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Title Annotation:BACK TO BASICS
Author:Smith, Bill
Publication:American Gunsmith
Date:Jul 1, 2018
Words:1910
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