Primers - Large Rifle Primer Study

A Match Primer Study in the 30-06 Cartridge
By Germán A. Salazar
This article was originally published in the September, 2008 issue of Precision Shooting

This article is a continuation of the work begun in “A Match Primer Study in the 6BR Cartridge” (Precision Shooting, June, 2008, p. 80). It may be worthwhile to review that article prior to reading this one as much of the historical background and procedural information applies to the tests presented here. In this article we will examine a good variety of modern primers, as well as some primers that are 30 to 60 years old. Among them are the Winchester 115, in the 1940’s considered to be a soft and accurate primer and the German made RWS, a hard to find primer with a great reputation in the current era.

While the 30-06 is not seen on the firing line of competitive Highpower events with the frequency of days gone by, it remains an excellent vehicle for this test series for a number of reasons. Foremost among these is the sheer volume of reference data that exists in the literature of the time regarding primers, loads and general accuracy levels in the 30-06. By this, I refer to the data generated at the Frankford Arsenal and at the Lake City Army Ammunition Plant. Further, while the 30-06’s popularity has declined in this era of the .223 “Highpower” competitor, its accuracy remains quite sufficient to win in a very competitive environment, and this rifle has done just that.

An Introductory Note
These articles regarding primers cover a very technical, often misunderstood and frequently overlooked area of ammunition performance. It is in no manner my objective to search for a “best” primer; rather the objective is to examine primer performance in a variety of ways in order to further our understanding of their characteristics. The articles contain many citations to previous work in the field, many from The American Rifleman which was for many years a top level source of technical information in the firearms field. Younger readers may not grasp how important it was to us, but in an age where computers were not a household appliance, technical articles in The American Rifleman were a primary source of information and the authors were men of significant experience in their field – it was not a magazine filled with fluff. I include citations to their work for the benefit of those with an extensive collection who might like to delve further into the topic and also to indicate the source of much of the historical data. I avoid opinion to the greatest degree possible in a technical article, preferring to hew closely to the history, facts and test results. Unfortunately, I cannot provide copies of the cited articles to readers as it would become an overwhelming task.

Test Equipment
The test rifle is a bit more modern than our 102 year old cartridge. The action is a modern, three-lug custom action with a Bartlein 5R barrel, 1:10" twist, 30" long, fitted by Clark Fay of Raton, New Mexico and stocked by Alex Sitman of Master Class Stocks in a composite prone stock. Although the rifle is normally equipped with Warner sights for match use, a Leupold BRD-24 scope was mounted for the accuracy portion of this test.

The new barrel was seasoned for 850 rounds prior to the beginning of the test. This process gave us a sense of the barrel’s accuracy with the LC 62 Match ammunition and various handloads, as well as getting us into the more accurate portion of the barrel’s accuracy life. (See: The American Rifleman: Life of a Rifle Barrel, P.H. Näätänen, March 1956 p.22; Barrel Life, Quintin Kernaghan and Col. B.R. Lewis, February, 1960 p. 38; Barrel Life, E.H. Harrison, July 1968 p. 81; Prolonging Match Barrel Life, E.H. Harrison, December 1970, p. 20; Facts of Barrel Life, Creighton Audette, January 1978 p. 54).

As in the previous article, pressure and velocity were measured using an Oehler 43 system with Bob Jensen manning the computer. I can’t say enough about Bob’s contributions to this project; his knowledge of ballistics, primers, loading and all ammunition related topics is tremendous; but in addition to all that, his day to day counsel and guidance have been the mortar that bound the bricks of the tests. Without Bob, it would have been a poorer test and a far less satisfying one as well. As before, fellow Desert Sharpshooters club members Jim Cobb and Nate Silverman also made significant contributions to the project, both at the range and in the shop.

Bob attributes much of his success as a Highpower competitor in the 1970’s and 1980’s, including his win in the Wimbledon Cup at Camp Perry in 1977 (200-10X), to his primer testing during that time. Details of Bob’s pioneering tests can be found in: Highpower Rifle Shooting Volume III, NRA, 1983, Handloading Techniques and Long Range Shooting Techniques, Bob Jensen, p. 60. A very brief summary of Bob’s findings in that early series of tests, is that those primers which produced the lowest average velocity in his specially built Winchester Model 70 test rig (which fired BBs powered only by primers) produced the best accuracy in actual ammunition. It is my modest aim to continue testing along the path that Bob identified.

Test Ammunition
We were able to obtain a good supply of Lake City 1962 Match ammunition to use as a baseline control, for both pressure and accuracy. The readings from the Oehler 43, as with most pressure measuring equipment, should be verified against a known pressure source and that is the principal role of this ammunition in our tests. We selected Lake City 1962 Match because of its long standing reputation for fine accuracy. It isn’t easy to find a large quantity of 46 year old ammunition, but we managed.

After a pilot run in 1961, Lake City Arsenal became the sole source of government manufactured Match and National Match .30 caliber ammunition in 1962 (National Match ammunition is headstamped NM rather than Match and was issued only at Camp Perry). New machinery and meticulous attention paid to optimizing the manufacturing process for accuracy rather than for production volume paid off with the most accurate 30-06 Match ammunition produced to that time. (See: The American Rifleman; National Match Ammunition, E. H. Harrison, Aug. 1962 p. 22; The Cal. 30 Cartridge in Match Competition, B.R. Lewis, Sep. 1969 p. 42). In fact, the facility itself went though some name changes to reflect its new role, changing from Lake City Arsenal to Lake City Ordnance Plant to the now familiar Lake City Army Ammunition Plant, all during 1962. The age of the 7.62 NATO cartridge was dawning in 1962, but the 30-06 did not go gentle into that good night. Though it was over 60 years old when last produced as a National Match cartridge, the 30-06 NM burned and raved at the close of its day, raging against the dying of its light by producing, in those final years, the best accuracy of its long and storied history. I hope Dylan Thomas fans will forgive my inept allusion to his poetry.

In order to conduct pressure testing, we need a load of known pressure to be used as a reference at each test session. In the case of the 6BR that was greatly simplified by Lapua’s assistance with modern factory ammo and components. In this series of tests, our pressure reference ammunition was the aforementioned Lake City 1962 Match; this is loaded with 48.1 grains of IMR 4895, the Remington 84M primer (very similar to the Remington 9 ½ ) and, of course, the Lake City 173 grain FMJ bullet. With a good supply of those components on hand, duplicating the load for pressure and velocity averages was fairly simple. We planned to conduct the primer test with this duplicate load.

Unfortunately, our duplicate load suffered from exactly the same problem as the Lake City ammunition: excessive variance, by today’s standards, in both pressure and velocity. The cause of the poor ballistic uniformity is no mystery, the 30-06 case is far from full with the factory charge of 48.1 grains of 4895 and the LC 173 is somewhat inconsistent in the length of its bearing surface. The lower level of uniformity, compared to our 6BR test, was not entirely unexpected, but when combined with the 30-06’s somewhat lower sensitivity to primer changes, it reduced the reliability of our results to an unacceptable degree. After running the full series of tests with this load, Bob and I made the difficult decision to scrap the results and begin again with a more suitable load.

Based on our experience shooting the 30-06 in competition for many years, as well as a brief test over the Oehler 43 to confirm that experience, we selected a load using Hodgdon’s H4350 and the Lapua 185 grain D46 bullet (NECO moly coated) as our standard components, still using Lake City 62 Match brass. The Lapua D46 is a full metal jacket, rebated boat tail match bullet that has been winning matches since the 1930’s. While its design may seem dated to some, its performance will change that opinion quickly. It is truly, what my friend Bill Otten calls “an industrial strength match bullet”. We compared two lots of the D46 one from the late 1950’s and one of current manufacture. There were no dimensional differences to be found and ballistic uniformity and accuracy were equally good with both. The tests were run with the older lot which Bob originally acquired from his old friend Roy Dunlap, a name doubtlessly familiar to many of you.

Primer Seating
Primer seating is a widely misunderstood, not to say disregarded, topic among many otherwise accuracy minded shooters. Many believe that as long as a primer fires, it has done all that it can do – this is wrong. I also hear and read reports of misfires attributed to primers when, in reality the person reloading the ammunition has either improperly seated the primers or has altered the firing mechanism of the firearm in such a manner as to decrease the energy of the firing pin’s strike below the level needed for reliable ignition.

With regard to this topic, we all share in the enormous good fortune that Creighton Audette chose primers as the subject of his final work for publication. (See: Precision Shooting; Primers, Chapter 1 through Chapter 6, Creighton Audette, October 1994 p. 48; November 1994 p. 38; December 1994 p. 77; January 1995 p. 19; February 1995 p. 46 obit. p. 8; March 1995 p. 24). While primer seating was not the exclusive focus of Audette’s series, he covered seating in ample detail, building a number of fixtures to test various primer seating methods and standards. He concluded that a primer must be seated fully and evenly, with some degree of compression of the pellet but avoiding damage from over-compression. This relatively straightforward conclusion came after a significant amount of testing and was not as obvious then as it now seems, being at odds even with primer manufacturers who advocated a specific amount of primer compression – yet offered no proof of performance nor seating method designed to provide that specific amount of compression.

Our three-fold objective, then, is to seat the primer fully, evenly and with some slight degree of compression. It would appear that most any tool can do the job and that is indeed the approach taken by most handloaders; but that too is wrong. A primer, after all, is not a digital switch with “on-off” function. Rather, it is a very analog component with a gradient of performance determined largely by the quality and consistency of the seating process and by the adequacy of the firing pin’s strike. In order to achieve the aforementioned three objectives, the tool must provide a great deal of “feel” to the user and must hold the case and primer in unchanging alignment. Further, the primer pocket must present a uniform and consistent seating surface. Finally, the user must devote sufficient care and attention to the process or all else is moot.

Audette gave us the following standard for a priming tool: “I think a little ingenuity in design could result in a primer seater where the part which holds the primer in alignment with the pocket, and through which the primer punch advances, could be moveable, so it would come hard against the case head as the punch is advanced. This automatically squares up the case. The punch is made so the amount of protrusion beyond the primer holder is adjustable and forward movement of the punch is limited by the holder, which comes up hard against the head of the case, as the tool is actuated. The distance could be set with feeler gauges. Or, there could be a series of thin washer-type shims to be inserted in the tool to give the compression desired for the primer height being used.” (Precision Shooting; Primers Chapter 6, Creighton Audette, March 1995 p. 24, at p. 26).

Sinclair and K&M currently offer priming tools which meet the design criteria set forth by Audette. I will save the long dissertation on primer seating technique and case primer pocket preparation for another time, but suffice it to say that if you use one of these two tools properly, and seat into a clean and uniform primer pocket, you are 90% of the way home (See also: Principles and Practice of Loading Ammunition, Earl Naramore, Chapter 40, Small Arms Technical Publishing Company, 1954).

Primer Flash Photos
As we discussed in the previous article, the search for the soft primer was certainly part of our investigation; in fact, we were, to a large extent, seeking to define the term and to determine if it remains relevant. We saw in the small rifle primer tests that a smaller visual flash typically resulted in lower muzzle velocity, lower chamber pressure, more uniform ballistics and better accuracy in the 6 BR cartridge. Our working hypothesis, based on those results as well as Bob’s earlier work, was that the modern definition of a soft primer is one that embodies the following qualities: smaller visual flash, lower muzzle velocity and lower chamber pressure than those against which it is compared. One of our principal questions in this test was whether those characteristics would still result in better accuracy when the cartridge changed to the 30-06 which has approximately twice the powder capacity and twice the powder column length of the 6 BR.

The primer flash photos themselves have been the source of some discussion among those with whom we have shared them. In each picture you see not only the plume of superheated gas, but also the shower of sparks generated by powdered aluminum or other material which is added to the mix to help propagate combustion throughout the charge. While many see them as “seeing the formerly invisible” for the first time, others question whether the photos can show anything meaningful. Writing 25 years ago, Creighton Audette was in the doubters’ camp, having said in response to a question about primer flash photos that photographic film might not capture all of the wavelengths of light generated by each primer, making comparisons difficult (Highpower Rifle Shooting Volume III, NRA, 1983, Audette, p. 80).

Audette went on to say the following, which certainly fits the results we obtained:

“The ignition of powder by the primer consists of two basic mechanisms. One of them is a hot gas which may or may not show up [on photographic film] to a high degree. The other is the incandescent particles of priming compound. Some primers show sparks like the 4th of July while others show just a little faint glow. In my opinion its unfortunate we don’t have the old Frankford Arsenal 70 primers to play with because they developed a mild ignition to the charge. It was an ignition accomplished mostly with gas and very few incandescent particles. If you snap one of the magnum primers we have today in a dark room by putting an empty one in a gun, you’ll get a flash that’s gone out two feet beyond the muzzle with sparks coming from it similar to those that come from a grinding wheel when you lean on it with a piece of steel. Testing primers is a very difficult proposition. A lot of people have spent a lot of time at it and no one has come up with a good way of doing it yet” (Highpower Rifle Shooting Volume III, NRA, 1983, Audette, p. 80).

Audette’s words from 25 years ago still carry a great deal of weight; primer testing is quite difficult and the results are not necessarily of universal applicability. However, we believe that the combination of digital primer flash images, velocity, pressure and accuracy testing, when viewed in combination, can give us a strong sense of direction in finding the most suitable primer for a given application. Study the primer flash pictures in this article and you will see as wide a range of visual flash and incandescent particles as were shown in the small rifle primer article. Interestingly, though perhaps not surprisingly, the large and small primers from each manufacturer tend to produce similar types of flash. Note that the Russian PMC primers produce a small flash with no particles, Federal tends toward small, no-particle flash in their older primers, but the more recent ones are more like Winchesters with a mid-level flash and plenty of particles. Then there’s Remington, always the blow-torch of the group, in this case joined by RWS and some others.

Statistical Firing Tests
Table 1 summarizes the instrumented firing test of the twelve primer types used for this article. This is quite a few more types than the five primers we covered in the first article, but given the opportunity to test a broad range of primer types and vintages, we believed the additional effort to be worthwhile.

A careful study of the primer flash photos and the related data in Table 1 will show that the correlation between flash size and pressure which we have previously noted is neither exact nor universal, but it is a strong one. Generally speaking, a lower level of visual flash corresponds to a lower level of pressure and velocity. Other statistical measures, however, notably the standard deviation (SD) of both pressure and velocity do not necessarily follow the same trend. Perhaps we’re seeing the need for more flash in a larger case.

The obvious question is how one interprets all of this data. As Long Range competitors, we have typically looked for loads that produce uniform velocities as measured by low SD of velocity and to a lesser degree, low extreme spread (ES) of velocities. Certainly this is a useful goal when fine tuning a load, but when conducting a broad survey of primers, it probably isn’t enough. For obvious reasons of practicality, all of the firing tests were conducted with a single load. It is inconceivable that this load is ideal for all of the primers tested. However, while perhaps not ideal, it is a useful load in that it is in the normal pressure range for the cartridge and it is reasonably uniform; therefore, it suits our needs well.

We begin our process of data interpretation by bearing in mind Bob’s early tests with the primer-powered, BB firing Model 70. Those test showed that the primers which produced the lowest velocities with reasonable SD in the Model 70 “BB gun” were the most accurate at 600 to 1000 yards when loaded in .308 ammunition. In fact, our own testing with the 6BR showed that the most accurate primers at 600 yards were those which produced the lowest velocities. Remember, you can always adjust velocities with the powder charge, if needed for accuracy reasons; the issue isn’t low velocity per se, but rather the primer’s contribution to the velocity. The reason for this is that the primer contributes energy to the system in a manner quite disproportionate to its size; however, the precision with which priming compound is measured and dispensed into the cups is somewhat less than the precision with which a careful handloader measures and weighs powder charges. Accordingly, a high energy primer with (for example) 5% energy variability, will have a greater absolute effect on total energy variability than will a lower energy primer having the same 5% variability. A milder, softer primer is a more consistent primer. All of this assumes that the primer in question has sufficient energy to reliably ignite the powder charge in the relevant environmental conditions and sufficient cup thickness and hardness to resist blanking under the pressure generated. The magnum primer has a useful purpose, for instance, but firing mid-size cases on the target range in the summer is not that purpose.

The data show a fairly wide range of performance among the primers. Pressure ranged 4,600 psi; from a low pressure of 57,100 psi (Win. 115) to a high of 61,700 psi (Fed. 215 Magnum). This last load is over the SAAMI specified average maximum pressure of 60,000 psi for the 30-06 cartridge. Muzzle velocity ranged 49 fps from a low velocity of 2816 fps (Win. 8 ½ -120) to a high of 2865 (Fed. 215 Magnum). Similarly, the SD of both pressure and velocity showed a wide range. Primers, like any other component, require testing before substitution; however, these tables should not be used as a substitute for your own testing as the data is valid only for the specific lots used and the load and rifle with which they were tested.

Primers matter, primers affect pressure, primers affect velocity and they can certainly affect accuracy. However, the relationship of these characteristics is not perfectly correlated and there is enough unpredictability in them that testing is always called for when developing loads. Possibly the greatest error a reloader could make in interpreting this data is to assume that a primer’s effect on velocity is a good guide to its effect on pressure – that is flatly wrong. Cartridges develop pressure and velocity largely through the evolution of powder into a large volume of gas driving the bullet forward. While primers certainly generate superheated gas, the volume is much smaller than that produced by the burning powder charge. A primer which increases pressure does so largely by increasing the rate of change of pressure (the rise time) and taking it to a higher peak. While this will increase the total energy produced, and thus the muzzle velocity, it is not in direct proportion as this quick initial peak can’t sustain bullet acceleration in the same manner as an increased volume of powder generated gas.

A good example of the foregoing can be seen in Table 1, test numbers 28 and 29. You will note that the primer difference between the Federal 215 and the PMC generated a pressure change of 3,800 psi and a 40 fps increase in muzzle velocity. However, in additional testing (not shown in the tables) we found that a 1.0 grain increase in the powder charge with the PMC primer raised pressure 3,700 psi and velocity by 70 fps. Hopefully, the implications are clear: muzzle velocity generated by primers comes at the expense of an untoward increase in pressure and, often, a decrease in ballistic uniformity. The proper place to seek velocity is in the powder charge; the role of the primer is to provide a source of adequate, uniform ignition leading to greater ballistic uniformity.

Accuracy Firing Tests
We selected six of the twelve primers for accuracy firing tests. In order to narrow the field to a manageable number, we looked for those primers which generated velocity and pressure at the lower end of the range as well as relatively low SD and ES of both velocity and pressure. This is our working definition of a soft primer although it is a relative set of criteria, requiring comparison of many types in order to identify those which qualify. We also selected one of the hotter primers for comparison.

The primers selected for accuracy testing were the Federal 210, the PMC Russian, the CCI BR2, the Winchester LR, the RWS and the Federal 215. While we would have liked to test all of them, the realities of finding enough range time at 600 yards under reasonably consistent conditions dictated that we keep the number at five or six types. In any event, this portion of the testing is probably the least important in terms of exploration and discovery. After all, the load isn’t particularly tuned to any of the primers, the specific lots of components are very unlikely to be duplicated by anyone and there’s a reasonable element of human error involved in shooting prone, despite the best possible preparations. The objective of this part of the test is simply to observe the effect of greater or lesser ballistic regularity at mid-range distances with a modest number of shots. No firm conclusions should be drawn from this type of sample as it is far too small to be a reliable indicator of performance. If anything had been exceptionally good or exceptionally bad, we would raise an eyebrow but in this short test, nothing appeared at the extremes. Table 2 summarizes the accuracy firing results.

Some Concluding Thoughts
I like to imagine that in the days of the flintlock, there were occasional heated discussions at the town tavern over which quarry produced the best flint and how to best grasp it in the rifle’s jaws. That argument is still with us in a more modern context and hopefully we’ve illuminated some interesting aspects of the topic. However, sometimes it’s best to draw some qualitative inferences from the data so as not to lose sight of the objective amidst the tables and charts.

It was interesting to see in these tests that age apparently had little effect on the primers. The variations in performance seen among them had more to do with types and perhaps production lots than with age. The Winchester 115, which was mentioned by Audette as a soft primer produced reasonably low velocity and pressure, but not very uniformly; modern primers did a better job. We also saw an evolution over time in some brands of primers – some towards a softer primer, some towards a harsher primer. There simply is no substitute for testing each lot of primers; neither the brand nor the specific designation can be relied upon as being an accurate description of the primer’s characteristics.

The 30-06 appears to be somewhat less sensitive to primer changes than the 6BR which we used in the small primer tests. That is not terribly surprising when one considers that the 30-06 has approximately twice the internal capacity of the 6BR, thus reducing the effect on pressure of a given change in primer gas evolution. Nonetheless, the basic relationship seen in the 6BR tests held: primers generating lower pressure and lower velocity generally gave more ballistic uniformity and better accuracy.

We began the first article with reference to the soft primer of the corrosive primer era and its presumed beneficial effect on accuracy. I believe that we have demonstrated that a softer primer is beneficial to accuracy. Generally speaking, a primer with three characteristics: a small visual flash, relatively lower pressure and relatively lower muzzle velocity than its peers, is our definition of a soft primer that will maximize accuracy. Some primers embody one or two of those three characteristics and they may be acceptable in many loads, but for our purposes, all three must be met for the accurate characterization of a primer as a “soft primer”.

Having tested a broad sample of primers from the dawn of the non-corrosive era to the present, it is my opinion that the choices offered to the reloader today exceed those of the past in quality and in range of “power”. We have milder primers and stronger primers and generally speaking they are more uniform. While the tables in this article reflect the firing of a few hundred shots, in reality we fired over 1,500 rounds to gather the information presented herein. Quite a bit of it didn’t make the cut, but still broadened our understanding. Matching the primer to the load is critical for peak performance and never has the handloader had a more useful selection of primers than he has today.

Table 1: Statistical Firing Test
Load: LC 62 brass, Hodgdon H4350, Lapua 185 gr. D46 moly

Previous Article
A Small Rifle Primer Study

All contents Copyright 2012 The Rifleman's Journal