Precision Shooting 1-Part 1: The Basics of Your Rifle
Floating the Barrel
To “Free Float” the barrel means that the barrel does not touch any part of the barrel channel. The barrel channel and action area should be sufficiently larger than the running diameter of the barrel and action. This allows for better cooling of the barrel and also prohibits moisture build up in the stock as well as the collection of solvents that could cause the stock to warp. Warping, as previously mentioned, will change your zero.
Free floating the barrel basically involves opening up the Barrel Channel so that the barrel will have a minimum of 0.05 inch clearance. You can do this yourself by using a large wooden dowel and wrapping it with sand paper. You must make sure that it isn’t too large or you will open it up more than you want. When you are done, seal the sanded area with an epoxy mix. However, I recommend a competent gunsmith for these processes. They can hopefully be found in your area or through the stock manufacturers.
Length of Trigger Pull
The length of trigger pull is another variable that aids the shooter by customizing their settings so that the shooting position is not just more comfortable, but allows the tip of the finger (only) to be placed on the trigger. The length of trigger pull for shotguns is measured from the inside crease of your arm to the first crease of the first knuckle of your index finger. (When firing, the trigger should be pulled straight back.) If more than the tip of the finger is used, and the trigger is not pulled straight back, your finger can actually slightly push or pull the rifle to the left or the right upon ignition. The shooter wants a straight pull back on the trigger. HS Precision who manufactures synthetic rifle stocks makes a stock with an adjustable pull length. With rifles, the length of pull is measured by your own discression and what is most comfortable for you.
What you should know about your rifle barrel
As previously mentioned, free floating your barrel is an important aspect of accurate shooting. A free floated barrel allows for better cooling and aids in the maintenance of your stock. However there is more to your barrel than you might think.
Barrels are manufactured from either a chrome molly steel, or 416R stainless steel. Some come blued, sand blasted or coated with Teflon or other treatments, and some exotics come wrapped in Kevlar. I do not recommend fluting your barrel and here is what Shilen has to say, “Fluting a barrel can induce unrecoverable stresses that will encourage warping when heated and can also swell the bore dimensions, causing loose spots in the bore. A solid (un-fluted) barrel is more rigid than a fluted barrel of equal diameter.
All rifle barrels flex when fired. Accuracy requires that they simply flex the same and return the same each time they are fired, hence the requirement for a pillar bedded action and free floating barrel. The unrecoverable stresses that fluting can induce will cause the barrel to flex differently or not return from the flexing without cooling down a major amount. This is usually longer than a shooter has to wait for the next shot. The claim of the flutes helping to wick heat away faster is true, but the benefit of the flutes is not recognizable in this regard until the barrel is already too hot”. Whatever barrel you utilize, they all have several things in common; they all have “lands” as well as Harmonic Vibrations, and stress.
The lands are the raised areas between the grooves that are cut into the interior of the barrel, which allows the bullet to rotate down the barrel and spin as it leaves the muzzle. This aids in the stabilization of the bullet which in turn provides for better accuracy. There are three basic machining processes that barrel manufacturers use to machine the rifling into the barrels and are as follows.
The modern broach method of rifling uses a hardened steel rod with several cutting rings spaced down the rod. Broaches can be over 16 inches long and because they have several cutting rings, they are referred to as gang broaches.
Probably the most common method used today to rifle barrels is button rifling. Button rifling uses a different approach to forming the grooves in the barrel. A button is a very hard steel plug that is forced down an unrifled barrel. The grooves are then formed in the barrel under very high pressure. The pressure created to form the rifling in the barrel hardens and polishes the inside of the barrel.
Hammer Forged Rifling
The newest mechanical method of rifling barrels is accomplished through a process called hammer forging. Hammer forging produces a type of rifling called polygonal rifling. A hardened steel mandrel is produced with the shape of the rifling formed on its outer surface. The mandrel is inserted into a barrel blank and the outer surface of the barrel is machine hammered. The hammering forces the barrel material down against the mandrel and the inner surface of the barrel takes on the shape of the mandrel. The mandrel is then removed from the barrel and the outer surface of the barrel is cleaned up. Just as in the other types of rifling, polygonal rifling can have different patterns. The most common polygonal patterns are 6/right and 8/right.
In a process that eliminates the conventional machining of metal, rifling is formed by wet-etching the interior of a barrel under an electric current. The metal inside the barrel is actually eaten away or dissolved to create grooves in the barrel. An electrode (cathode) that has metal strips in the shape of the rifling is placed in the barrel (anode) and the assembly is submerged in a salt solution. An electric current is applied and the electrode is moved down the length of the barrel and twisted to create the spiral shaped grooves. As the current travels from the barrel to the electrode metal is removed by electrolysis thus forming the grooves in the barrel. This process creates the rifling in the barrel very quickly and does not require consumable tooling.
All rifle barrels have their own “sweet spot”. Just like a baseball bat or golf club. When the ball is hit on the right spot of the bat or club, it is a solid hit and the ball reacts by traveling further in the air. Your rifle barrel is similar as when the correct combination of powder and bullet are fired down the barrel, its sweet spot is found and the harmonic vibrations are less. Barrels with less harmonic vibrations produce less chatter when the bullet goes down the bore. It is smoother and stabilizes the bullet better. This is why some factory cartridges work better in your rifle than others and hand loads work the best. With hand loads you are able to experiment with different kinds of bullets, powders, and powder charges and oftentimes 2/10th of a grain of powder will make a difference in group size.
Most stock rifles come with production run barrels. These are not all that bad, however they have not been manufactured with the great care as the after market match grade barrels have. All match grade barrels have been hand lapped and some even stressed relieved. Not to mention that the holes are drilled as perfectly on center as possible. Some of these match grade barrel manufacturers are; Shilen, Douglas, Lilja, Schneider, Rock and Hart.
Steel expands 1 millionth of an inch for every one degree of temperature increase. When a non stressed relieved barrel begins to heat up, the steel begins to react. This causes slight changes in the barrel, causing it to shoot a different point of impact after about the third or fourth bullet is fired; and continues to change throughout the shooting session. In addition to the slight amount of warpage, your barrel is flexing each time the trigger is pulled and we want the barrel to flex back or return to its original point position. The process for stress relieving a barrel is Heat treating it, and that takes place in an industrial oven. The heat releases the stress in the metal by aligning the metal's molecules.
The crown of the muzzle basically protects the lands and grooves from being damaged. If you were to drop your rifle onto the front of the muzzle you could hypothetically chip or scratch them. This would or could cause the bullet to leave the barrel with an uneven burst of gas. This in turn would have a destabilizing effect on the bullet, making it less accurate.
You can now see how the components of your rifle begin to work together, and how important each factor is becoming. Right now is where some of you will say, “this is all too complicated and all I want to do is go out and hunt”. Perhaps you do not have time for all of this. But it basically comes down to owning a rifle that is just correctly built, and maintained. Maintenance is the easy part. You just check the torque settings; keep your rifle clean and in good operating condition. But you must first have a decent platform to work from. A well built rifle will shoot three rounds, ˝” groups or less with factory ammunition at 100 yards. This in turn means that at 1000 yards, your groups (without the effects of wind) will be 5 inches. Realistically you should be able to hit within a ten inch pie plate or better. That is what you and your rifle are capable of.
There are several other factors that finish up this section. They include scope mounts, scopes and cleaning methods.