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TUNE YOUR MINI-14 by James Mason

From Guns & Ammo/March 1987

With the introduction of the Mini-14 rifle, Sturm, Ruger wrought a major coup in the field of firearms. This lightweight .233 caliber rifle displaced the M1 Carbine in the hearts and minds of many American shooters.

The scale, weight, and military presence of the Mini-14 made it an instant hit... the .223 cartridge being vastly superior to .30 caliber M1 Carbine ammo. Few firearms have so instantly filled a market niche as the Mini-14.

Over the years, shooters have come to realize a few shortcomings in the Mini-14. The factory corrected one of these when it brought out the Ranch Rifle by equipping it with scope blocks and low side ejection of fired cases. The other concern has to do with accuracy. The Mini-14 was never designed for match shooting and delivers 3 to 4 inch groups at 100 yards; throw in the usual "human factor" and that score reads 4 to 6 inch inconsistent groups.

The average Mini-14 owner is not necessarily an accuracy buff, but the latterday generation has come to expect smaller groups from all rifles. Many shooters are adept at doing minor repairs on their own guns, and tuning the Mini-14 for its performance potential makes a good weekend project for the off-season.

With appropriate references to "kitchen table" gunsmithing, there are three areas where work on the Mini-14 will pay off in tighter groups. This is a serious project that, while not overly difficult to perform, requires attention to detail from the amateur gunsmith.

Stock bedding, Trigger group modifications, and sights are the areas that best reward diligent attention. Tailored handloads can also contribute toward accuracy and will be discussed, but this is outside the reaim of a gunsmithing activity. Besides, a lot of Mini-14 shooters do not reload, and depend upon commercial or remanufactured ammunition and foreign military fodder.

A discussion of some Mini-14 design realities helps put this project in perspective. As was mentioned above, the Mini-14 was not designed as a match gun. It has a thin, low-mass barrel with gas-impulse actuation. The barrel will vibrate from firing alone, but gas impulses against the relatively heavy inertia operating slide cause further disturbances to barrel nodal movement.

The Mini-14 gas system uses a hollow, fixed piston though which propellant gases impinge on the operating slide. There is no contained, modulated piston stroke. So, the reaction to the gas pulse induces a slight bending movement on the mid-barrel section-enough to disturb normal barrel vibrational rhythms.

The Mini-14 has a good quality birch stock, which is quite stable, but not overly stiff, due to the thin wall sections around the receiver and fore-end. New guns are factory fitted to provide some stiffness, but after shooting a couple of thousand rounds, setting of parts makes the stock fit a fairly loose proposition. Rebedding can restore that stiffness and assure support for the Mini-14's operating elements.

Trigger pull characteristics on all military rifles leave a lot to be desired. The safety aspects of two stage pulls need not be sacrificed, but a properly regulated trigger job can produce a 4 to 4 1/2 pound letoff that will do more to reduce the effect of the human factor than anything else, with the exception of a better sight system.

The coarse-adjusted military sight on the factory Mini-14 is suited to the original design objectives of the rifle. It is okay for a rifle designed to shoot 3 to 4-inch groups. But, adjustment stops and aperture design limit it for more demanding shooting. Millett Sights (16131 Gothard Street, Dept. GA, Huntington Beach, California 92647) understands the needs of more demanding Mini-14 shooters, and have adopted their Series 100 Sight to the Mini-14 and other assault-type rifles. The result is a first-rate replacement peep sight that meets the needs for realizing the performance potential of the Mini-14.

Positive, 1/3-minute click-adjustments on the Millett sight allow for both windage and elevation. A large match-style eyepiece shields the eye from glare. The standard .080-inch aperature (.050-inch is optional) provides a crisp, clean sight picture; the aperature hole is reverse tapered, like top-grade match sights, so no "tunnel effect" distort aperture edges. The Millett sight base fits directly into the Mini-14 receiver and is secured by a single throughpin-a simple, easy installation once the factory sight is removed. The installation makes a handsome complement to the Mini-14 receiver.

The factory Mini-14 front sight blade is an exposed, serrated ramp with a slightly tapered silhouette. There are several possible replacements available for this front sight unit. The Choate front sight and flash hider unit makes a good replacement choice and was installed on our conversion. The Choate front sight blade is a military post with "ears". The flash hider is of the bird cage type, and is solid on the bottom, providing muzzle stability during firing.

A well-bedded stock adds to stiffness and support of the operating elements. While new Mini-14's may fit well, continued firing will loosen up the stock and receiver union. By using a non- shrinking stock bedding compound such as Accraglas glas, support for receiver legs, the operating rod guide channel and the stock ferrule can be reinforced. Dismantling the stock allows removal of the stamped sheet metal recoil stop that fits inside the receiver magazine opening A thin coat of bedding compound under these supporting structures adds to the stiffness of the midsection of the stock and assures minimal creep of the recoil stops. After treating metal parts with parting compound, lightly apply epoxy to the wood then replace the recoil stop in the stock and tighten the side screws. Let this piece cure overnight.

Next, remove the stock ferrule and the sheet metal action slide guide. Butter the stock seating area for these parts and replace the metal. Again, be sure to coat the metal with parting compound before contacting the bedding compound.

Using silicone parting agent, spray the inside surfaces of the gas piston collar assembly and butter the outer surface of the stock ferrule with compound. At the same time, spray the receiver legs and bottom of the receiver with parting agent. Butter the receiver leg channels in the stock to fill in the area below, in front and to the sides of the receiver legs where they seat in the stock. Assemble the barrel/receiver group in the stock using a large rubber band to hold the stock and receiver together. Let this work cure overnight after wiping off any excess bedding compound that oozes out of joints. A little oozing shows a proper amount of compound; don't overapply, but use enough to fill all the voids. Failure to use parting agent can result in embarrassment. You might permanently bond the stock and the receiver together!

Separate the stock the next day, then carefully chisel out any excess ridges on the inside of the stock. Small bubbles in the work may be refilled. Reassemble the stock and insert and secure the trigger assembly. Observe any looseness of the trigger assembly. This may require additional bedding under the flat contact pad on the bottom outside edge near the middle of the receiver.

Use parting agent on the receiver bottom, then apply bedding compound on the stock surfaces adjacent to the receiver pad. Reassemble the rifle, insert the trigger group, but close the trigger guard down only to about 1/2 inch away from its hooking point. Let the epoxy cure, then clamp the triggerguard shut. This technique assured a very solid stock-to-barrel/receiver fit, necessary for consistent shooting accuracy.

Trigger work calls for smoothing burrs and surface roughness off of sear/hammerhook engagement surfaces. First disassemble the trigger group and arrange the parts so hard stoning of the contact areas can be done without altering engagement angles. Dressing hammerhooks and sear surfaces amounts to a few deft strokes only. As a rule, when people feel they have done enough, too much stoning has been accomplished. Overstoning will reduce trigger pull letoff weight to below 3 1/2 pounds, making trigger release unpredictable in an autoloading rifle. Too light a pull can cause the gun to "double" or "triple" due to the rocking motion of recoil and return-to-battery of the enertia slide. A 4 to 4 1/2 pound pull is ideal with little or no sensation of cheep. The classic two-stage military pull characteristic should definitely be maintained.

A word of warning is in order here. Trigger adjustments demand experience and a definite "feel" for the job. A poor trigger job can ruin an otherwise good rifle. It is possible to make the piece unsafe if the adjustment is botched. Amateurs who may do other gunsmithing perfectly well may have no particular skill at trigger adjustment. Unless individuals are experienced at regulating a trigger pull, the job is best done by a trusted professional. The rewards of a well regulated trigger are essential for rifle accuracy, so take your Mini-14 trigger group to a competent local gunsmith or put it in a padded mailing envelope along with a check or money order for $35.00 and send it to: Poway Gun Works, 13168 Poway Road, Dept GA, Poway, California 92064 to have it done right.

Field testing comes after the bedding, trigger regulation and sight installation. The test rifle was first fired with some surplus Lake City Arsenal '67 vintage ammunition. Center zero was established at 25 yards with intermediate (50 yards) firing and later 100-yard groups fired off the bench. Shooting was done in early morning with very little of no crosswind.

Our early groups were erratic and disappointing, but, as firing continued, the rifle settled into its bedding and groups converged on zero. Early cold-barrel groups were respectable in the 2-3 inch size. But groups "walked" with a vertical string as the barrel heated up. Once the bedding was seated and the gun heated uniformly, the best groups appeared.

After things settled down and became consistent, a switch to Remington .223 commercial ammunition produced groups up to the full potential of the gun. The best six-round group measured 1.6 inches at 100 yards. It would be good to try Winchester and Federal Commercial loads in individual guns to observe the result. None of these brands were available on our test day, however. Nobody can complain about 1 1/2 minutes of angle with a Mini-14!

The Choate front sight is investment cast and the top post corners are very slightly rounded. Flat filing squares up the post. Millett's sight base with the Choate post combination made the gun shoot high-about 12 inches high at 100 yards. Millett has since modified their base to correct for this.

Bedding effects are intrinsic to such good groups. But the trigger job and crisp, effective Millett sights were appreciated as aids to practical accuracy. Shooter confidence imparted by this tuning was evident shortly after firing began.

Custom handloads would probably shrink groups further, but the effects would not necessarily contribute as much as if the loads were fired in a bolt-action rifle. The need for cannelured bullets and crimping with self-loading ammunition, along with loose chamber dimensions of self-loader, limits accuracy contributions of carefully assembled custom loads in the Mini-14.

So, there it is! An attainable project for the Mini-14 owner who wants to get the most out of his rifle. For just a couple of evenings' time and the price of materials, you can upgrade the rifle's handling characteristics as well as accuracy and performance. And, for riflemen who care, there is the self-satisfaction of having made their Mini-14 perform.