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WARNING:     I have been advised by a correspondent that, "The procedure Harris described to grind the front face of the slide where it contacts the gas block (to improve accuracy) will not work on the current Mini-14Ranch and Mini-30. The lugs on the slide are rounded and cannot restrain the slide on their own. I would suggest you edit out this section or post a note or someone may wind up ruining their slide. If you have any questions e-mail me at rob100@mailandnews.com ".
[ I have not personally confirmed the accuracy of this warning, but will leave it posted unless and until I learn otherwise. As usual, you should NOT make any modifications to a firearm unless you are skilled in such gunsmithing work and know exactly the results that will be produced. --PAZ ]

When I was at Ruger I tested hundreds of Mini 14 rifles of all configurations, conducting audit shoots of normal production, as well as R&D testing of the full-auto AC556, AC556 and the experimental XGI rifle in .308 Win, and assisting in the development of the Mini Thirty in 7.62x39.

To be COMPLETELY honest I was disappointed with its accuracy when compared to the M16A1 and A2 rifles, with which I am very familiar. The Mini 14 gives reasonable performance for an American-made rifle in its price range, and is safe, serviceable and realiable. It just isn't all that accurate. You can find individual rifles which shoot well, but these are statistical aberrations. We tried to test a large enough sample of rifles to pick "good" ones, then painstakingly took them apart and gaged every part to see if we could tweak tolerances or make design changes which would significantly improve accuracy without increasing production cost. It couldn't be done. We did learn a few things, however.

The long run average group size for standard Mini-14 rifles fired from a test stand is about 4-5" for ten-shot groups with M193 or M855 ammunition of "average" quality [at 100 yards? -- PAZ], producing an acceptance Mean Radius of 1.6-1.6" at 200 yds from a test barrel [Ed has an error in there somewhere -- PAZ]. The M16A1 or A2 do this at 200 yards from a machine rest. I believe the biggest factor in Mini-14 accuracy is irregular contact between the gas block and the face of the slideblock, welded to the slide handle (aka operating rod).[from Ed's comment below that Minis are tested for a 2" group at 50 yards (1" radius), we can infer that the Mini is expected to shoot a 4" group at 100 yards, or an 8" group at 200 yards. Thus, the Mini-14's 200 yard Mean Radius would be 4"--twice as bad as expected from Military AMMO (2.00" mean radius max. avg. at 200 yards), presumabably fired from a test rig of some kind. -- PAZ]

If you disassemble the rifle and inspect the face of the slide block and the rear of the gas block assembly, you may find that the face of the slide block strikes one side or the other of the gas block, rather than making a uniform and symmetrical imprint. This asymmetrical contact causes fliers. The fit-up can sometimes be improved by grinding 0.005-.010" off the face of the slide, so that with the slide fully forward, a .001" shim can be inserted between the slide block and gas block and be clear all the way around. This way the forward motion of the slide is stopped by the right locking lug in the cam pocket of the slide handle, rather than by the slide block slamming against the gas block, as is the case with the M1 Garand rifle.

I caution against removing the gas block, because these are installed in a fixture at the factory to insure proper alignment. There is a small bushing in the gas block which locates it on the barrel. You must be careful not to lose this. This is why the gas block screws are staked in place on newer guns. [Once the gas port and bushing recess are drilled, I cannot see how there can be any variation in alignment of the gas block -- PAZ]

The condition of the muzzle crown is important as well as the straightness of the barrel. Sometimes the barrels are bent when pressing the front sight on. Usually they catch this at the factory and they correct them if it causes fliers in the range, but since they only shoot indoors at 50 yards, for a 2" group, the accuracy standards are more in keeping for a plinking rifle than for the serious accuracy enthusiast.

The Mini-14 chamber conforms to U.S. dwg. #8448649, which is used for the M16A1 chamber. It has a .225" cylindrical ball seat with a slight freebore. I do not believe the GI chamber causes any inaccuracy in this type of rifle, because I have fired thousands of rounds in heavy test barrels with this chamber which gave fine accuracy. For an accuracy load I suggest 21-22 grs. of 4198 (either IMR or Hodgdon) with the 52 or 53-gr. Sierra bullets loaded to 2.25" OAL, or 23-23.5 grs. of H322. The 52-gr. Nosler solid base also is quite accurate.

The Mini-14 Ranch Rifle was made in .222 Remington for the export market to France, Belgium and Italy where civilians are not allowed to own firearms of military caliber. Overruns were sold in the U.S.

And here's another guy's idea:

This idea was passed to us a long time ago, before the new proliferation of accurizing services for these rifles was available. Yes there are lots of neat things that can be done for these rifles now to enhance their potential, but those solutions also entail time and outlay of cash. The idea presented here works! It has literally cut group sizes nearly in half on many of the guns we have done it to and it requires no gunsmithing services.

The gas block assembly at the forward part of the forend, which is held together with four screws from the underside, is the focus of our attention. Remove the four screws, and then remove the top part of the gas block. Then remove about .030" of metal from the mating surface of that block by running it over a piece of plate glass or plate iron (a very flat very stable surface) covered with 320 grit wet/dry sandpaper. By removing the metal from the mating surface you create the necessary gap for tuning, as you will see below.   [If there already is an adequate gap, it may not be necessary to remove as much as .030" of material. --PAZ]

Now that you have accomplished the removal of approximately .030" from the upper gas block assembly, reassemble the unit with this procedure. When tightening the four screws, use an inch/lb. torque wrench to VERY UNIFORMLY tighten them all with the same torque [I believe 16 INCH-pounds is the proper value--PAZ], and simultaneously use a feeler gauge to make sure that the gap between the block halves is uniform side to side as they are torqued down.

This little procedure puts pressure on the barrel from the gas block very uniformly, and equalizes that pressure, especially as the barrel heats up from repeated firing. Simple as it sounds, it works! No, maybe not a complete cures all, but certainly a no cost enhancement.