Rifle Accuracy, Sub MOA Requirements

Action tuning (blueprinting) is the process of making all the parts that make up the action square and true to the bore. First the locking lugs of the bolt must be lapped to insure even solid contact with the locking surfaces in the receiver. When finished the lugs should have equal contact area and contact should exceed 80%. This is accomplished using professional lapping compounds which produce smooth even surfaces.  Finally we put the action on a precision mandrel and turn it in the lathe to face the front of the receiver square to the bore.  Note the areas in the picture that are pointed out, the light spots are where the metal was in full contact during bluing, the dark areas were exposed to the bluing salts, obviously contact was not even.

Barrel Lapping is available for new barrels upon request.   Lapping the bore can offer more uniformity, velocity, and accuracy. This process removes the small burrs and marks left in the bore from the machine process. It also polishes the bore, which reduces fouling. A side benefit is that, there is little or no break in for a lapped bore. Which saves lots of time, money, and tedious cleaning.  Many of the best barrels are lapped by the manufacturer, McGowenHart and Lilja are three examples.  

Barrel Fit is the next consideration. The barrel must be set up on the lathe so that it is centered perfectly on the bore. Centering the barrel on the bore insures that it will be mounted squarely in the action. The shoulder will be exactly 90 degrees to the bore and the threads will be concentric to the bore, all essential to accuracy. Equally as important is the crown. It also must be concentric to give best accuracy. Over the years we have tried many styles of crowns at many different angles to the bore. Some work better than others but the bottom line is always the same, if it is concentric it will be accurate. 

Trigger Jobs can do more for accuracy than you might think. These days the factories are shipping guns with trigger pulls of five to eight pounds. To add insult to injury they include lots of sear engagement  (shooters call that ‘Creep’).   A trigger job will minimize sear engagement and bring the pull to a consistent weight that will give the shooter better control over the moment of ignition.

Bedding methods varies a little from one action to the next. The best method on average is to free float the barrel and bed the action. This can be accomplished through either pillar bedding and glass bedding. Pillars are made from metal usually aluminum, the purpose is to add a support to the stock so that it cannot be crushed by the action screws. The pillars also add stability to the bedding job. Glass bedding is the most common method used. Fiberglass and epoxy are used to bed the action of the rifle. This adds stability and protection from humidity. Proper bedding requires an understanding of the pressure points of the action and the methods that will provide the best support and results. A good bedding job will improve accuracy.

Ammunition is a major factor in accuracy for any rifle.  Accurate ammunition is a product of good reloading skills and tools. There are many makers of reloading dies. Quality varies widely from one manufacturer to the next. All will work to produce usable ammunition. Accurate ammo requires better quality dies. Just like the rifle, the dies must be concentric in order to be accurate.  Think of it this way, if you were to draw a 12 inch long line on a piece of paper with a ruler held firmly down you will get a single clean line from end to end. What happens if you stop every inch and pick the ruler up, replace it on the paper, and continue the line? Likely no matter how careful you are the line will not be perfectly straight. When we reload ammo we are picking up the ruler with every component used and with every process executed.  That is why its so important to make sure everythint is just right when loading for accuracy.

This is by no means a complete discussion of rifle accuracy but its a good start.  I recommend that you take your reloading manuals down off the shelf and read some of the articles that they contain.  You will be amazed how much good advice on how to load the best possible ammo is already on your shelf.

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Filed under accuracy, ammo, Firearms, hunting

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