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Reloading the Winchester .308 for Accuracy

Summary

Fully assembled .308(7.62mm X 51mm) caliber round.

Reloading, for the purposes of this article is defined as the assembly of the individual components of a rifle cartridge to create fully assembled ammunition. The purpose of reloading is to obtain the most accurate cartridge for the individual rifle. This goal can be achieved by following the reloading steps provided here and adjusting the components until the maximum accuracy is obtained.

Case prep

Case Cleaning

The first step in any reloading process is the cleaning of the brass casings. The brass can be tumbled in any kind of cleaning media (pieces of walnut, corncob, stainless steel, etc.) to remove unwanted powder waste and dirt from the brass. This is important for providing a clean foundation for assembling the rest of the individual components. Cleaning the inside of the case helps provide consistent volume and creates consistent cup pressure which has an effect on velocity.

Lubricating the case

All cases must be lubricated to decrease wear and tear on the reloading press. This step has to be completed before sizing and de-priming the case. Failure to do so can damage the press or one of its components.

Sizing and De-priming

Typical single stage reloading press.

After a round is fired, the brass case expands and must be resized. Each case must be sized to provide the proper fit into the chamber of the rifle. The length of the case must be checked after sizing to ensure that proper tolerances are maintained. Volume and cup pressure are directly influenced by case length. The cases should be trimmed to the proper lengths if needed. Sizing and decapping the case usually happen at the same time with most reloading presses.

Primer Pocket and Flash Hole Cleaning

At this point the exterior of the brass case should be clean and ready for further preparatory work. The primer pocket should be reamed to remove excess carbon for proper fit. Reaming the flash hole is also important to ensure uniform ignition from the primer in every cartridge of ammunition produced.

Primer pocket with the flash hole in the center after the round has been fired.

Deburring

The deburring process is a quality control step that removes small burrs from the mouth of the brass case. These burrs and imperfections can cause scratching inside the reloading press and inside the chamber of the rifle. This can damage the rifle and reloading tools. It can also lead to a loss in accuracy over time.

Case Selection

All of the cases have been through enough preparation at this point to undergo a final case selection process. Selecting a case is based on the following three criteria:

1. Only cases of the same brand and preferably the same manufacturing run should be used. Even though it is a .308 case, the internal volume may vary between different brands of brass.
2. Minor defects in the brass cases that cannot be corrected in the preparation processes should be removed to obtain the highest levels of uniformity among the cases to be loaded.
3. Any case with defects such as: split necks, signs of head separation, deep scratches, etc. must be removed. These defects can be detrimental to safety and possibly lethal to the shooter in extreme cases.

Priming

Priming the case is one of the easiest and least involved steps in reloading. The primer can be inserted into the case using a number of different tools (reloading press, hand tool, etc.). The priming process is complete as long as the primer has a tight fit and is flush with the surrounding case.

Powder Charge

Adding powder is one of the most important steps in the reloading process, not only for the accuracy of the round, but for the safe firing of the round. Each different type of powder comes with a tested set of manufacturer tolerances and exceeding these tolerances is not recommended. A good example is the 175 grain SMK (Sierra Match King) bullet, loaded using IMR 4064 (powder) in a Federal brass case. The minimum load of powder is 41.5 grains and the maximum is 45.6 grains. Its always a good rule to perform what is known as a "load workup", starting at 41.5 grains and testing loads with increasing levels of powder. Each group of loads should be tested at 100 yards for accuracy in groups of five to ten rounds. After firing, the cases should be inspected for potential defects due to high pressure or other signs of deformation. A primer that bulges out from the bottom of the case is one of the most common defects to see during inspection.

Bullet Seating

Inserting the bullet into the brass case with a reloading press is known as bullet seating. The depth at which you seat the bullet can effect cup pressure, velocity, and what is known as bullet jump. Bullet jump is the free travel space from the chamber to the rifling of the barrel. Too much bullet jump can decrease accuracy and consistency.