The Importance of Rifle Case Preparation

The Importance of Rifle Case Preparation

by Morris Smith October 15, 2016

Second to the firearm, case preparation or case "prep" is one of the most important contributors to accuracy.  When it comes to handloading, you can consider case prep to be a foundational step in creating highly accurate rifle ammunition.  Without it you will not achieve the results you might otherwise be able to. Precision handloading is all about consistency and uniformity and good case prep is the foundation of producing accurate and consistent ammunition.  In this article I will discuss how I perform my case preparation for precision rifle ammo.  Keep in mind that I reload my rifle ammo with the purpose of shooting steel plates out to 1000 yards.  Depending upon your personal application, you may choose to do more or less.  An F class shooter, for example, will have different requirements of his or her ammo than a 100 yard deer hunter.  My precision rifles are capable of sub MOA accuracy, so I generally expect ½ MOA or better groups out of those rifles.  Always keep the intended application in mind.  It should also be noted that all brass, whether it be brand new, once fired or 10x fired, requires preparation.

 

Step 1: Selecting the correct brass

The first step in case prep for precision handloading is to make sure you're using high quality or "good" brass. By this I mean that it is uniform and consistent, with the internal volume, wall thickness and dimensions of each piece being the same or very close to the next piece. The primer pockets should also be able to handle more than a few loadings before they become stretch to the point that primers become loose. Brass produced by different manufacturers will typically possess different internal case volumes, which in turn will produce inconsistent velocities, so if loading for precision results it is important to sort your test loads by headstamp.  In some cases, even the same brand of ammo can have varying internal volumes, so those brands may not be the best choice for competitive, precision shooting.

So how does one identify “good” brass? Assuming you are buying one brand of brass you can take the cases and weigh them.  Good brass will have a consistent weight or minimal variations in weight. This is not the ideal method to use as things other than internal volume can affect the weight of a case, but it is a common and generally accepted method. A more accurate way is to fill each case with water and measure the volume of water it holds.  This is, in my opinion, a slow and tedious method that is also prone to user errors. The third (and my preferred) way of doing it is to look at what has been done before by other experienced reloaders; buy the brand or brands that are known to be consistent.  These include the likes of Lapua, Norma, and believe it or not, Winchester (at least in 308). I previously used Lapua brass exclusively for my precision rifle ammo, but switched to Winchester brass which provides the same level of accuracy out of my hand loaded rounds at a significantly better price point.  Losing $1 brass cases every time you go to the range is enough to drive a cost conscious guy like myself crazy. In any event, after doing a ladder test load workup with the Winchester brass I was able to achieve the same level of accuracy as I did with the Lapua brass, although it was with a different size powder charge. It is worth pointing out that anytime you change a component of your handloads you need to do a new load workup in order to find the best measures. It's also worth noting that you can achieve very good results with commercially purchased once fired brass and it provides another way to significantly reduce overall reloading costs.  There are, however, some additional steps to undertake when using it. Very often when purchasing once fired brass it is sold as mixed headstamp. If the brass you purchase is of the mixed variety then you should sort the brass by headstamp in order to obtain the most consistent results possible. Some people will also then sort by weight and, in the case of LC headstamped brass, sort by the year of manufacture which is also printed on the head of the casing. If you are using military brass you may also have the additional step of removing the crimp in the primer pocket. Fortunately, brass sold as fully-processed usually has this step already completed for you.

 

Military Crimp

 

Step 2: Case cleaning and prepping

Cleaning brass is required in order to protect your dies from carbon, dirt and other debris that form on and in the case when fired. Effective case cleaning does not require a golden mirror like finish that resembles or surpasses factory brass. Some handloaders get hung up on how polished and shiny their brass is, when all they really need to do is remove the build-up that is present.  After all, the intention is to load it and shoot it again. Shiny brass is not a reflection of your prowess as a hand loader. You could literally clean the brass in your kitchen sink with soap and water or even wipe each piece of brass with a cloth by hand in a pinch. In practice however, most of us use automated methods.  There are several types of machines that clean brass casings: rotary tumblers which use liquid and stainless steel pins, ultrasonic cleaners which also use liquid, and of course, the reliable vibratory machine with some sort of dry media (usually ground walnut and/or corn cob). All of these methods work though, so there's no need to overthink it.

 

Brass Tumbler

 

A good case prepping station is also a worthwhile investment.  They can save quite a bit of time, especially when prepping new brass.  They can make an otherwise tedious, time-consuming process much more manageable.  That being said, I personally use a set of Lyman hand tools.  They are slower, but just as effective.  There are also trimming, chamfering and deburring hand tools that can be used to perform each of these steps, and they'll get the job done, but the downside is that they are very time-consuming. This is one area where I would recommend automation or power tools. If you are going to purchase a powered trimmer (either a motorized unit or one that mounts to a drill) do yourself a favor and purchase a trimmer that also chamfers and deburrs.  I currently use a Giraud Triway trimmer.  For about $100 it is money well spent and time saved.

 

 Lyman Case Prep Center    Giraud Trimmer

 

Even new brass should be sized because brass often comes from the factory with inconsistent sizing and or length. The case mouth is also sometimes “dinged up” while in transit. Sizing the brass resets everything to SAAMI spec and allows you to ensure that the brass is in spec and uniform in length.  Remember that the brass will stretch in length when you size it so it is important that you size it before checking the length against spec in anticipation of trimming.

Once the brass is sized, check its length. If it is too long then take out your powered trimmer cut it to spec while chamfering and deburring. If the brass is in spec and does not require trimming, then chamfer and deburr it with separate chamfer and deburring tools. In the future, you will only need to trim your brass when it "grows" past the specification.  Depending upon the caliber and load this could be every firing or every 3rd firing or so.  This is why it is important to always size and check the length prior to loading.  Chamfering and deburring is only required when the brass is trimmed.  Some reloaders trim every firing to maintain consistent length, even when it is within the acceptable range.  Personally, if I have one piece of a group that is out of spec then I'll trim, chamfer and deburr all the rounds in that batch.  For me it’s just easier than having to take the time to measure each piece.

 

Step 3: Addressing the primer pockets

Primer pockets only need to be tended to prior to the initial loading.  If you are using military brass with crimped primer pockets swaging will be required.  There are several swaging and reaming tools that can be used to accomplish the job.  If you are using commercial brass then you can skip this step.  Again, if your brass does require this step it only needs to be done once.

Primer pocket uniforming is accomplished with a primer pocket uniformer.  This creates a uniform primer pocket depth to enable identical primer seating depth, this too can be accomplished with either a case prep station or a hand tool.

Flash hole deburring is required to clean up any burrs left in the case around the flash hole during the manufacturing process.  The burrs occur because many brass manufacturers punch the flash hole which often leaves burrs. Some manufacturers, such as Lapua, drill the hole which leaves no burrs.  Deburred flash holes ensure consistent ignition of the powder charge. It is also worth mentioning that many flash hole deburring tools index off of the case mouth which is another reason to make sure case lengths are consistent.

A note about neck turning...some reloaders choose to do it, but for my purposes it is probably not worth the time.  If I were loading to compete in F class or bench rest shooting, then yes, perhaps the extra effort would provide a return on the investment. But for PRS-type tactical matches or 1000 yard steel ringing I don’t see the value.

Finally, brass prep is just the first step in producing accurate rifle ammo.  Keep in mind that "accurate" is a subjective term and defined differently by each shooter. For me accurate ammo is sub-MOA, and I am generally not happy unless I am able to shoot under ½ MOA, but my purposes are certainly different than those of your typical deer or elk hunter.

 



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