220 lines
12 KiB
Plaintext
220 lines
12 KiB
Plaintext
#65
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TUNE YOUR MINI -14 by James Mason
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From Guns & Ammo/March 1987
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With the introduction of the Mini-14 rifle, Sturm, Ruger wrought a
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major coup in the field of firearms. This lightweight .233 caliber
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rifle displaced the M1 Carbine in the hearts and minds of many
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American shooters.
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The scale, weight, and military presence of the Mini-14 made it an
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instant hit... the .223 cartridge being vastly superior to .30 caliber
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M1 Carbine ammo. Few firearms have so instantly filled a market niche
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as the Mini-14.
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Over the years, shooters have come to realize a few shortcomings in
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the Mini-14. The factory corrected one of these when it brought out
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the Ranch Rifle by equipping it with scope blocks and low side
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ejection of fired cases. The other concern has to do with accuracy.
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The Mini-14 was never designed for match shooting and delivers 3 to 4
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inch groups at 100 yards; throw in the usual "human factor" and that
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score reads 4 to 6 inch inconsistent groups.
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The average Mini-14 owner is not necessarily an accuracy buff, but the
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latterday generation has come to expect smaller groups from all
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rifles. Many shooters are adept at doing minor repairs on their own
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guns, and tuning the Mini-14 for its performance potential makes a
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good weekend project for the off-season.
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With appropriate references to "kitchen table" gunsmithing, there are
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three areas where work on the Mini-14 will pay off in tighter groups.
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This is a serious project that, while not overly difficult to perform,
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requires attention to detail from the amateur gunsmith.
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Stock bedding, Trigger group modifications, and sights are the areas
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that best reward diligent attention. Tailored handloads can also
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contribute toward accuracy and will be discussed, but this is outside
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the reaim of a gunsmithing activity. Besides, a lot of Mini-14
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shooters do not reload, and depend upon commercial or remanufactured
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ammunition and foreign military fodder.
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A discussion of some Mini-14 design realities helps put this project
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in perspective. As was mentioned above, the Mini-14 was not designed
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as a match gun. It has a thin, low-mass barrel with gas-impulse
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actuation. The barrel will vibrate from firing alone, but gas impulses
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against the relatively heavy inertia operating slide cause further
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disturbances to barrel nodal movement.
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The Mini-14 gas system uses a hollow, fixed piston though which
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propellant gases impinge on the operating slide. There is no
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contained, modulated piston stroke. So, the reaction to the gas pulse
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induces a slight bending movement on the mid-barrel section-enough to
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disturb normal barrel vibrational rhythms.
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The Mini-14 has a good quality birch stock, which is quite stable, but
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not overly stiff, due to the thin wall sections around the receiver
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and fore-end. New guns are factory fitted to provide some stiffness,
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but after shooting a couple of thousand rounds, setting of parts makes
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the stock fit a fairly loose proposition. Rebedding can restore that
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stiffness and assure support for the Mini-14's operating elements.
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Trigger pull characteristics on all military rifles leave a lot to be
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desired. The safety aspects of two stage pulls need not be sacrificed,
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but a properly regulated trigger job can produce a 4 to 4 1/2 pound
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letoff that will do more to reduce the effect of the human factor than
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anything else, with the exception of a better sight system.
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The coarse-adjusted military sight on the factory Mini-14 is suited to
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the original design objectives of the rifle. It is okay for a rifle
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designed to shoot 3 to 4-inch groups. But, adjustment stops and
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aperture design limit it for more demanding shooting. Millett Sights
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(16131 Gothard Street, Dept. GA, Huntington Beach, California 92647)
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understands the needs of more demanding Mini-14 shooters, and have
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adopted their Series 100 Sight to the Mini-14 and other assault-type
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rifles. The result is a first-rate replacement peep sight that meets
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the needs for realizing the performance potential of the Mini-14.
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Positive, 1/3-minute click-adjustments on the Millett sight allow for
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both windage and elevation. A large match-style eyepiece shields the
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eye from glare. The standard .080-inch aperature (.050-inch is
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optional) provides a crisp, clean sight picture; the aperature hole is
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reverse tapered, like top-grade match sights, so no "tunnel effect"
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distort aperture edges. The Millett sight base fits directly into the
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Mini-14 receiver and is secured by a single throughpin-a simple, easy
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installation once the factory sight is removed. The installation makes
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a handsome complement to the Mini-14 receiver.
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The factory Mini-14 front sight blade is an exposed, serrated ramp
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with a slightly tapered silhouette. There are several possible
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replacements available for this front sight unit. The Choate front
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sight and flash hider unit makes a good replacement choice and was
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installed on our conversion. The Choate front sight blade is a
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military post with "ears". The flash hider is of the bird cage type,
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and is solid on the bottom, providing muzzle stability during firing.
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A well-bedded stock adds to stiffness and support of the operating
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elements. While new Mini-14's may fit well, continued firing will
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loosen up the stock and receiver union. By using a non- shrinking
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stock bedding compound such as Accraglas glas, support for receiver
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legs, the operating rod guide channel and the stock ferrule can be
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reinforced. Dismantling the stock allows removal of the stamped sheet
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metal recoil stop that fits inside the receiver magazine opening A
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thin coat of bedding compound under these supporting structures adds
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to the stiffness of the midsection of the stock and assures minimal
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creep of the recoil stops. After treating metal parts with parting
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compound, lightly apply epoxy to the wood then replace the recoil stop
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in the stock and tighten the side screws. Let this piece cure
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overnight.
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Next, remove the stock ferrule and the sheet metal action slide guide.
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Butter the stock seating area for these parts and replace the metal.
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Again, be sure to coat the metal with parting compound before
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contacting the bedding compound.
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Using silicone parting agent, spray the inside surfaces of the gas
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piston collar assembly and butter the outer surface of the stock
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ferrule with compound. At the same time, spray the receiver legs and
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bottom of the receiver with parting agent. Butter the receiver leg
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channels in the stock to fill in the area below, in front and to the
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sides of the receiver legs where they seat in the stock. Assemble the
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barrel/receiver group in the stock using a large rubber band to hold
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the stock and receiver together. Let this work cure overnight after
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wiping off any excess bedding compound that oozes out of joints. A
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little oozing shows a proper amount of compound; don't overapply, but
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use enough to fill all the voids. Failure to use parting agent can
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result in embarrassment. You might permanently bond the stock and the
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receiver together!
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Separate the stock the next day, then carefully chisel out any excess
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ridges on the inside of the stock. Small bubbles in the work may be
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refilled. Reassemble the stock and insert and secure the trigger
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assembly. Observe any looseness of the trigger assembly. This may
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require additional bedding under the flat contact pad on the bottom
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outside edge near the middle of the receiver.
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Use parting agent on the receiver bottom, then apply bedding compound
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on the stock surfaces adjacent to the receiver pad. Reassemble the
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rifle, insert the trigger group, but close the trigger guard down only
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to about 1/2 inch away from its hooking point. Let the epoxy cure,
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then clamp the triggerguard shut. This technique assured a very solid
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stock-to-barrel/receiver fit, necessary for consistent shooting
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accuracy.
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Trigger work calls for smoothing burrs and surface roughness off of
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sear/hammerhook engagement surfaces. First disassemble the trigger
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group and arrange the parts so hard stoning of the contact areas can
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be done without altering engagement angles. Dressing hammerhooks and
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sear surfaces amounts to a few deft strokes only. As a rule, when
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people feel they have done enough, too much stoning has been
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accomplished. Overstoning will reduce trigger pull letoff weight to
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below 3 1/2 pounds, making trigger release unpredictable in an
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autoloading rifle. Too light a pull can cause the gun to "double" or
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"triple" due to the rocking motion of recoil and return-to-battery of
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the enertia slide. A 4 to 4 1/2 pound pull is ideal with little or no
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sensation of cheep. The classic two-stage military pull characteristic
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should definitely be maintained.
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A word of warning is in order here. Trigger adjustments demand
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experience and a definite "feel" for the job. A poor trigger job can
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ruin an otherwise good rifle. It is possible to make the piece unsafe
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if the adjustment is botched. Amateurs who may do other gunsmithing
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perfectly well may have no particular skill at trigger adjustment.
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Unless individuals are experienced at regulating a trigger pull, the
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job is best done by a trusted professional. The rewards of a well
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regulated trigger are essential for rifle accuracy, so take your
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Mini-14 trigger group to a competent local gunsmith or put it in a
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padded mailing envelope along with a check or money order for $35.00
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and send it to: Poway Gun Works, 13168 Poway Road, Dept GA, Poway,
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California 92064 to have it done right.
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Field testing comes after the bedding, trigger regulation and sight
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installation. The test rifle was first fired with some surplus Lake
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City Arsenal '67 vintage ammunition. Center zero was established at 25
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yards with intermediate (50 yards) firing and later 100-yard groups
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fired off the bench. Shooting was done in early morning with very
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little of no crosswind.
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Our early groups were erratic and disappointing, but, as firing
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continued, the rifle settled into its bedding and groups converged on
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zero. Early cold-barrel groups were respectable in the 2-3 inch size.
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But groups "walked" with a vertical string as the barrel heated up.
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Once the bedding was seated and the gun heated uniformly, the best
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groups appeared.
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After things settled down and became consistent, a switch to Remington
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.223 commercial ammunition produced groups up to the full potential of
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the gun. The best six-round group measured 1.6 inches at 100 yards. It
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would be good to try Winchester and Federal Commercial loads in
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individual guns to observe the result. None of these brands were
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available on our test day, however. Nobody can complain about 1 1/2
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minutes of angle with a Mini-14!
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The Choate front sight is investment cast and the top post corners are
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very slightly rounded. Flat filing squares up the post. Millett's
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sight base with the Choate post combination made the gun shoot
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high-about 12 inches high at 100 yards. Millett has since modified
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their base to correct for this.
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Bedding effects are intrinsic to such good groups. But the trigger job
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and crisp, effective Millett sights were appreciated as aids to
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practical accuracy. Shooter confidence imparted by this tuning was
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evident shortly after firing began.
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Custom handloads would probably shrink groups further, but the effects
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would not necessarily contribute as much as if the loads were fired in
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a bolt-action rifle. The need for cannelured bullets and crimping with
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self-loading ammunition, along with loose chamber dimensions of
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self-loader, limits accuracy contributions of carefully assembled
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custom loads in the Mini-14.
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So, there it is! An attainable project for the Mini-14 owner who wants
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to get the most out of his rifle. For just a couple of evenings' time
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and the price of materials, you can upgrade the rifle's handling
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characteristics as well as accuracy and performance. And, for riflemen
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who care, there is the self-satisfaction of having made their Mini-14
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perform.
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=======================================================================
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