I wrote this article a few years ago. It was published in the .50 caliber shooters newsletter, but in no other format that I'm aware of.
I thought I might share it with everyone here. As this article is a few years old, some of the tools, equipment and techniques discussed may have been improved upon since, or may be obsolete.
Take it for what it is, take it for what you can use... enjoy.
Hand-loading for Accuracy
This article will discuss the components and procedures necessary, as well as their relationships to one another and to the rifle used, to produce an accurate center-fire rifle cartridge.
With the exception of the belted magnum group of cartridges, which require different resizing methods and some of the more complicated wildcat chamberings, this information in this article applies to any center-fire bottleneck rifle cartridge.
The information and procedures contained herein are intended for the hand-loader of, at least intermediate experience. Beginning re-loaders should initially content themselves with learning the basic concepts of producing safe, reliable ammunition.
There may be some items of interest to the advanced hand-loader, and at the very least, may provide alternate methods and theories to consider. My approach to learning is to listen to everything, consider it all, and ultimately, try the things that make sense.
As an aid to explaining some of the steps presented, a “reference” rifle and cartridge will be used.
A benchrest rifle, consisting of a Stolle “Panda” action, H&S Precision graphite stock, Jewell competition trigger and H&S “10X” match barrel chambered in a “tight neck” 6 PPC. This particular rifle has produced 5 shot groups as small as .042".
The 6 PPC, as used by the vast majority of benchrest competitors, is the most consistently accurate cartridge developed to date, due in part, to its balance of case dimensions, powder capacity and bullet used.
This rifle and chambering was selected as a reference because it will require the most steps to produce a finished cartridge.
Not all rifles are capable of producing sub MOA groups at 100 yards. It is up to the reader to determine if all or any of the information provided is of value in their particular application.
Components.
Bullets.
The bullet selected provides, arguably, the greatest single contribution to accuracy.
Begin by selecting a bullet that is the correct weight and/or length for the rifle barrel’s rate of twist. “Twist ratio” is the distance in inches the rifling rotates one complete turn around the inside diameter of a barrel. The barrel’s twist is what imparts the stabilizing “spin” on the bullet, too much or too little for a given bullet and stability and consequently accuracy, will suffer.
A needlessly high rate of twist will reduce accuracy because it will accentuate any imbalance in the bullet. An insufficient rate of twist and the bullet will not stabilize adequately to remain, in simple terms, “point on”.
Numerous articles have been written about the effects different rates of twist have on bullets in relationship to their diameter, length, potential velocity and weight. Virtually all barrel and bullet manufactures offer readily available twist data based on bullet weight, intended velocity and caliber. The best advice I can provide is to try the slowest twist recommended for a specific bullet weight or, inversely, the heaviest bullet suggested for a given twist that will be sufficiently stabilized.
A word of caution is in order when using heavy bullets. Deep seating long heavy bullets to accommodate a box magazine’s interior length will alter the internal capacity of the cartridge case. Refer to an appropriate reloading manual in determining safe powder types and charge weights.
The 6 PPC reference rifle is equipped with a 1:14" twist barrel. This twist was selected because, of the possible choices for use with a 68 grain bullet, arguably, the most popular bullet weight for the
6 PPC, it should offer the best combination of stability and accuracy.
As air density also has an effect on stability, in that dense air can upset a marginally stabilized bullet, a slightly faster 1:13" twist could have been chosen if the rifle were to be continuously used in cold climates and/or lower elevations. The simpler solution of course, unless blessed with a selection of otherwise identical barrels of differing twist rates, is to adjust up or down slightly on the bullet weight to accommodate climatic or geographic changes.
The next thing to consider is the type of bullet used. Will a match bullet be more accurate than a hunting bullet of the same weight and caliber? Statistically speaking, yes. Why? Because match bullets are made to a higher standard in regard to jacket concentricity, finished weight, finished dimension and rotational balance. Certainly, there are instances of a particular rifle and hunting bullet combination with the ability to produce the occasional one hole group, but to consistently put 5 shoots into the same ragged hole, group after group requires the consistency of a match bullet. In .22 and .30 caliber alone, there are well over 100 possible choices of match grade bullets from bullet makers both large and small, in weights for every available twist.
Primers.
A primer is a primer, right? Wrong! Like any component available to the reloader, there are standard quality and match grade primers. To go into the details of primer manufacturing would require a separate article, but suffice to say, some are made more accurately than others. Not that the differences are great, it’s just that match primers are, much like match bullets, made with closer tolerances. In selecting a primer for the 6 PPC, I look to what is the most popular among winning benchrest and high-power competitors. Match primers from Federal, CCI and VihtaVouri are among the most common used in those disciplines, and for good reason, they are consistent.
Propellant (Gunpowder).
The choice of which gunpowder to use can be simplified greatly. Choose a powder that gives adequate velocity, but more importantly, fills the case. A partially filed case allows the powder to shift and be distributed in a random fashion as the cartridge is handled or disturbed by recoil. This means that when the primer ignites, how the powder burns and how pressures develop will vary. Consistency, in regard to powder selection, will be improved from shot to shot as the case is filled closer to 100% capacity.
When deciding on a powder, I suggest referring to all reloading data available and cross-referencing that data for the cartridge selected. Some reloading manuals provide valuable information on load density, others for bullet seating depth, still others indicate best powder choice for accuracy within specific parameters such as bullet weight or barrel twist.
VihtaVouri N-133 is the preferred powder for the 6 PPC. Once again, in an attempt to not reinvent the wheel, this powder is used because it is one of the most popular among successful benchrest competitors using the 6 PPC cartridge. A small grain, extruded type powder, it meters very precisely through a measure and, within safe pressure guidelines, fills the case to 95% plus capacity while delivering superior uniformity.
Unlike the majority of re-loaders, benchrest competitors will reload their ammunition at the range, during the course of the match. This is done for two reasons; one is to control variables as they occur. Adjustments to powder charge weight, bullet seating depth, neck tension and bullet weight can be made to accommodate changes in wind, temperature, barometric pressure, humidity and elevation. Reason number two is that benchresters use only a small number of cases, usually 15 to 25 for an entire event, and must continually reload them.
Why not preload enough cases for the entire match? Because to improve the odds that every bullet fired will go into the same hole, they will take a quantity of raw, unfired cases, select the most identical ones from the lot, then weigh, measure, machine and fine-tuned them until they are for all intents and purposes, identical. From that number, any case, which does not send its bullet into the group, will be immediately discarded.
The second discrepancy from conventional reloading, is that in benchrest competition, powder is dispensed directly into the primed case from a precision measure; no scales are used at the range. Scales are only used initially to make a “powder chart” or “graph” indicating what amount of powder will be dispensed when the measure’s micrometer dial is set to a selected number. The shooter, during previous practice sessions, has established a range of usable powder charges, within safe pressure limits, and will adjust the measure to accommodate variables as previously stated.
Using a repeatable, consistent technique to throw the individual charges, variations in powder weights delivered to the case are typically no more than one tenth of a grain.
The Case.
The cartridge case is the one component that, no matter how good it is, can be made better. The modifications detailed in the upcoming pages are those required to produce a case of competition quality. Lesser quality cases may be used, acceptable tolerances broadened, or some of the uniforming steps not taken but the finished results would be unacceptable to the individual trying to achieve the best possible accuracy.
Begin with a quantity of new or once fired cases. Purchase the best quality cases you can afford. Price is sometimes a good indicator, from brand to brand, of the inherent quality of the case.
The most important thing to look for is consistent case wall thickness.
Consider what competition shooters use, as those that are successful seldom skimp on the quality of brass. The better the quality of raw case, the better the finished product will be.
In the 6 PPC chambering, the most popular are the Lapua .220 Russian cases. Although expensive, these are considered to be the finest quality available for this application. As a parent cartridge, they must be sized up to 6MM, (.243 caliber) then fire-formed to the final 6 PPC dimensions. The Sako 6 PPC case is popular as well, and does not require any forming steps.
There are several manufacturers who produce match cases. For example, Federal Cartridge makes the high quality, Gold Medal Match case in all the popular civilian versions of NATO military chamberings such as .223 REM and .308 WIN.
Norma Precision produces cases that are, although not listed as match grade in their advertising, of exceptional consistency.
Different case brands, and even lot-to-lot variances of a single brand can vary in overall wall thickness. This particular point will be referred to again, later in the article.
Case Preparation.
Please read and reread this section before attempting any case uniforming procedures that are unfamiliar. Any attempts to achieve perfection require tools, preparation and patience. The minimum tool requirements are listed below.
A primer pocket “uniformer”. Not a scraper!
An inside flash hole de-burring tool.
A flash hole reamer.
A case length trimmer.
A case mouth inside/outside de-burring tool. Also referred to as a chamfering tool.
An outside neck turning tool with a neck turning/expander mandrel appropriate for the caliber used.
An expander body. This tool holds the turning mandrel in the loading press, necessary for a separate sizing procedure.
A metal dial caliper.
A powder measuring scale, preferably electronic, graduated in 0.1 grain increments.
A tubing micrometer, graduated in .0001" increments. (An acceptable alternative would be a case wall thickness gauge such as the RCBS “Casemaster” or NECO case gauge)
All these items are available from Sinclair International (
www.sinclairint.com) or a similar precision shooting supplier. Most re-loaders will already have some of these tools.
Once the case selection is made, they must be measured and weighed. Using the tubing micrometer or case wall thickness gauge, measure the thickness of the brass, at the neck, in four places or every 90°. Cases with a variance of greater than .001" should be discarded if they are to be used in competition. An inconsistency of not more than .002" is satisfactory for non-competition use.
Now weigh the remaining cases. The acceptable difference in weight is an arguable point but as a general rule of thumb it should not exceed 0.5% of an individual cases weight. Once the cases are sorted by thickness and weight, proceed to the next step. (Save the culls, they can be used for test and tool set-up instead of the matched cases)
When a case is manufactured, the primer pocket and flash hole are “punched” through. This process can result in a number of inconsistencies which all require correction. The previously mentioned Norma Precision drills the flash holes in most of their cases in an effort to eliminate some of these imperfections.
Begin by cutting all the primer pockets to a uniform depth. This is done for two reasons, to ensure that the relationship of the primer to the firing pin is constant, and to provide a flat surface for the anvil legs of the primer to seat against. Should a case show no indication of being cut in the pocket base, discard it to the cull pile. When preparing a large quantity of cases, an adapter is available to put the uniformer into a cordless screwdriver.
The next step is to check the I.D. of all flash holes. Most cases have a .080" flash hole. Any found undersize should be drilled or reamed to ± .001" of the standard diameter. The Lapua .220 Russian case has a small .060" flash hole and actually must be reamed to .0625" to accept the passage of a standard de-capping pin, or a special .059" de-capping pin must be used.
Where the flash hole comes through on the inside of the case is the next area of concern. When a flash hole is punched, a ragged burr may be left inside, around it’s circumference. These burrs vary from case to case and cause a non-uniform distribution of the flame generated when the primer ignites, in turn causing inconsistent powder combustion.
There are two types of inside flash hole de-burring tools. Some have a stop shoulder at the cutting end and will cut to the correct depth, regardless of overall case length. Others, such as the RCBS tool use an adjustable collar that indexes on the case mouth. If using the latter, then all cases must be trimmed to an equal length and de-burred prior to de-burring the flash holes. Remove only enough material to make the area around the flash hole smooth and even, with a slight chamfer. Refrain from turning a straight flash hole into a large funnel, it is not advantageous to do this and may weaken the case.
The most common case length trimmers are the bench-mounted types such as the RCBS and Forster units, which hold the case by its head in an adjustable collet. A floating shaft with a piloted cutting head is inserted into the case mouth and rotated until the shaft’s adjustable stop bottoms against the tool body.
Use a cull case for set-up. Trim to the SAAMI recommended case length or, with the aid of a “chamber neck length gauge”, an accurate measurement can be made of the barrel’s chamber neck length and the cases trimmed accordingly to fit that chamber. Don’t forget to de-burr the inside and outside of the case necks.
Before continuing, a little bit about chambers. There are essentially four types of rifle chambers, not counting wildcats. The first, a standard SAAMI chamber, will be somewhere between the minimum and maximum dimension specifications for a given cartridge. The second type, a “loose” chamber, or a chamber at maximum specifications, may sometimes be referred to as a “military” chamber; these chambers in a military rifle are designated differently. For example, a .223 REM has the NATO metric designation of 5.56X45 in a military rifle. This extra clearance allows the cartridge to fit and fire in the chamber even if both are dirty or the cartridge case is slightly damaged. A case fired in a military chamber will rarely fit a standard or smaller chamber without full length resizing due to the excessive stretching that occurs to the case in both length and diameter. The third, a “match” chamber is reamed to the minimum specification of the SAAMI guidelines and may also have a shorter than normal throat or “lead” to accommodate a specific bullet type.
The fourth type is the custom chamber, typically minimum SAAMI specs for the case body, a “tight neck”, under SAAMI specification and, like a match chamber, a specific throat dimension.
Parts two and three coming up...
C