Confession is Good for the Soul
M.L. (Mic) McPherson
Along about 1995, more than a quarter-century ago as I write this (2022), the fine folks at Norma invited me to participate in their moose hunt. I was honored to join them in that annual Swedish tradition, but I was far more excited at the opportunity to spend time at the Norma production facility and working in the Ballistics Laboratory there.
I was well prepared for several important projects the Chief Ballistician at Norma and I had planned. And, I came up with half a dozen other interesting things to study while I was there.
Among the former were three main projects. First, comparing the internal ballistics of the 6.5/60 SMc and the 6.5-284 Norma, and, to the extent this was possible, doing so scientifically. Second, comparing the internal ballistics of naked bullets and properly moly-plated bullets, again, to the extent this was possible, doing so scientifically. Finally, to study the internal ballistic influences of variations in bullet seating depth. I’ll cover those studies in some detail in this article.
The latter, included several minor projects, to answer nagging ballistic questions I’d long had. Those projects were interesting to me and to the ballistician, but I’ll not review those here.
Christer Larsson, then Chief Ballistician at Norma (now retired), was kind enough to work with me for more than one week, well into the evening each day. He had to do this to be able to do all his regular work and then help me with the tests I wanted to do. His boss, Norma CEO, Torbjörn Lindskog, was kind enough to give him permission to do so, and he explicitly gave us the run of the facility.
First day, Christer gave me the grand tour. He showed me every aspect of Norma production. He showed me the retired tooling and machinery of decades past; the bigger equipment stored neatly in a barn; the smaller tools shelved in one room inside the production plant. And he introduced me to many of his fellow employees. This was a grand experience for me.
Very early that day, in which we ultimately spent more than ten hours wandering around the Norma plant, while I asked questions and he answered, an inevitable question arose.
How Important is Quality to Norma?
Skipping ahead a bit, I’ll tell a story of something that happened the fourth day I was at the Norma plant. Christer and I were still busy with projects but he needed a break from the intensity of my enthusiasm to get things that were important to me done, imagine that. Along about ten in the morning, he got a call. After a short conversation, he hung up the phone and explained that there was a minor problem with a new set of case forming dies. He had been asked to join in on a meeting among folks involved with die production, case manufacturing, and quality control.
He said, “You might enjoy this too. You are welcome to join us.”
So, we walked a few doors down from the lab and entered the room with the optical comparator equipment. They had that set up, focused on the interior of one of the dies involved in the several steps in drawing a simple brass disk into partially finished 300 Winchester Magnum cases.
The comparator sat at one end of a room that was about 30-feet long. By that point in my visit, I was beginning to be able to follow technical conversations in Swedish, I immediately gathered that there was a problem with the interior contour of the die. I looked at the image on the wall screen and noted hash marks indicating some scale. Next lull in the conversation, I asked, “So what is the scale on the screen?” Christer responded, millionths of an inch.” As he said this I was staring at the display.
I spun my head and said, “Millionths?” He replied, “Yes.”
I again looked at the screen. What it showed was a symmetrical divot in the interior surface of the tungsten-carbide die that was about 100-millionths of one inch in length (one ten-thousandths of one inch), about 50-millionths of one inch wide, with a maximum depth of about 6-millionths of one inch.
After ten or fifteen minutes of discussion, with everyone calmly offering their thoughts. The final statement before that meeting adjourned, loosely translated from Swedish to English, was: Although such a modest imperfection could not possibly matter to the overall quality of the finished product, because this is Norma, we will discard that [expensive — thousands of dollars to produce] die and make one that is correct. They all agreed, and that was that.
If the question was: Does quality matter to Norma? I had my answer.
Back to the Plant Tour: How I Solved a Serious Problem
At that time, Norma had been fighting a quality-control issue for more than a decade — soft case heads in some batches of cases. Generally, all case heads were always hard enough to allow loading in most chamberings, one time. The exception was Weatherby ammunition, loads at that, unusually high, pressure level might open the primer pocket of the cases with soft heads enough to cause a dangerous situation. In all other rifle cases used in chamberings generating normal modern rifle-cartridge pressure, the heads of the soft cases would expand enough upon firing to prevent reuse of the cases.
Such cases were useless to handloaders. This was stressful to Norma, because of liability concerns. Perhaps worse, the existence of occasional soft cases was ruining Norma’s long-standing reputation for having previously made, what were, among the best cartridge cases ever produced anywhere in the World. As the discussion in the previous section should elucidate, that was a reputation Norma had worked long and hard to earn.
This failing reputation was killing Norma case sales in the United States, and it wasn’t doing Norma’s reputation any good anywhere else! Sales had long-since began to lag, instead of continuing to increase, as had been the situation for many decades. And, Norma was having serious problems loading Weatherby Factory ammunition, it had to carefully test each lot of Weatherby cases and scrap lots with soft case heads, because, as noted above, Weatherby load pressures would cause case-head failures in the soft cases.
This was expensive, time consuming, and it interfered with normal production. Nothing good came of this. This problem was serious enough that it could well have eventually destroyed Norma, and I believe the folks there fully realized that fact.
So, of course, as Christer was showing me the case-production and quality-control processes, starting at the end (finished cases or loaded ammunition being boxed for shipment) and working our way back toward the loading dock, where the raw materials were delivered. Inevitably, at every stage of that extensive tour, we discussed the case-head-hardness issue.
Christer explained that not two weeks earlier, a metallurgical expert Norma had hired and paid $50,000 U.S., had finished a six-week stint at Norma, a period during which he had, supposedly, studied everything that could possibly explain the soft-case-head problem. He left Norma with his substantial check and nothing more than a long diatribe explaining that he could not find anything that would explain why Norma cases sometimes had softer than ideal case heads.
Christer explained that, at significant cost to Norma, this so-called expert had installed and monitored thermometers and anemometers that would tolerate temperatures in excess of 400-degrees Fahrenheit, in various places in the annealing ovens. Christer further explained that Norma had to scrap two large batches of partially finished cases, as a necessity to fulfill this so-called expert’s request to interrupt the annealing process, so he could test some other aspect of what was happening inside the annealing ovens.
We talked about this at length. This so-called expert had cost Norma the better part of $100,000, in lost production and fees, and he had accomplished absolutely nothing that in any way provided a single iota of benefit to Norma.
Eventually, Christer and I made our way to the loading dock, where a truck happened to be off-loading a new batch of brass sheets, as used to make cartridge cases. We watched that process and talked about why the brass sheets came in different thicknesses. Then we watched as scrap brass was loaded into the truck before the dock leader sign the paperwork, accepting receipt of a specific amount (in kilograms) of brass in sheets of specified dimensions; and the truck driver signed paperwork, acknowledging receipt of a carefully weighed amount of scrap brass.
As the truck pulled away, I turned to Christer and asked, “So, where’s the ISO certification for this batch of cartridge brass?”
Metallurgically, cartridge brass is a specific product. It is composed of 70% copper and 30% zinc, with the allowance for only minute quantities of specific impurities, such as sulfur.
Christer looked at me with a blank stare. After several awkward seconds of silence, he asked, “What are you talking about?”
I replied, “I’m asking about the document that certifies that the material delivered is cartridge-brass alloy.”
Christer turned a bit pale and replied, “We’ve never asked for anything like that. We order brass from, such an so, and they deliver it.”
We talked about this a while. I soon understood what had happened. Historically, beginning about 1908 when two brothers founded Norma in what is now Norway, Norma had developed a relationship with a brass supplier. Both Norma and the brass supplier fully understood that what Norma produced (cartridge cases) required extremely pure cartridge brass, and that is what the brass supplier always delivered. What was, effectively, a handshake agreement continued through at least two generations of employees at both companies. Norma placed an order for brass. The folks at the company filling that order knew this meant only the highest-quality cartridge-brass alloy and that is what they priced out and shipped to Norma.
Then, eventually the inevitable happened, the last person working at the brass supply company who knew anything about what Norma was using the brass for, and why it was critical that the brass it sold to Norma was appropriately pure cartridge brass, retired. The next time Norma ordered brass, the brass supplier filled that order with whatever it happened to have on hand that was close to 70:30 alloy, but without any consideration of the quantity or type of impurities contained in that particular brass alloy.
For almost any application, other than the production of cartridge cases, such brass would have been entirely adequate and fully functional. When used to make cartridge cases, just a few parts per thousand of certain impurities, such as sulfur, resulted in soft case heads, regardless of anything Norma did in an effort to assure the case heads were hard enough.
Try as you might, you simply cannot make functional cartridge cases out of bubble gum; Norma had long-since proven that!
So, in ten seconds, I solved Norma’s soft case head problem. And I just gave that information away! Not the first or last time I made such a generous financial mistake.
Thereafter, Norma required ISO certification on every product coming into its plant. Soon enough, the soft case-head problem was a thing of the past.
In fairness, I do want to note that, unlike several other companies for which I helped improve products or solve other problems, Norma was very generous, until Torb retired. Whenever I had a project, Norma always provided cases and propellants, very generously. Savage was the only other company that showed any gratitude. But, again, when the CEO at Savage retired, that generosity also essentially ended.
Back to the Lab
What makes me almost physically ill is the fact that I have managed to misplace all the data gathered in all the testing Christer and I did. I have it, I just cannot find it! If I could, I’d certainly include pictures of the pressure curves and show tables with specific data. Because I cannot do that, what I can do is present the conclusions and basic results.
The first and most important test to me was comparing the 6.5/60 and 6.5-284 chamberings. My intention was to design the 6.5/60 to have the same usable capacity as the 6.5-284. I did this, specifically so we could compare the two chamberings as fairly as possible.
I missed that design goal, slightly. With the 140-grain Hornady Spire Point bullets we used in our testing, seated 30/1000-inch off the rifling in each chamber, the 6.5/284, with the cases I had converted from Norma 416 Rigby cases, had 4% less usable capacity than the Norma 6.5-284 cases had. (All else being equal, this would account for a velocity difference of about 15-fps.)
Christer had an almost new 6.5mm barrel that had been chambered for the 6.5×55 and used enough for him to realize it was an unusually good barrel. After discovering that it seemed to be a particularly easy-to-clean barrel (suggesting excellent overall bore quality), he set it aside for my proposed and then planned 6.5/60 to 6.5-284 comparison testing.
I arrived at Norma with three custom chambering reamers made by Pacific Tool & Gauge:
A machinist took time from his busy schedule to rechamber the 6.5 barrel Christer had set aside, using the 6.5-284 reamer and throating reamer so the dummy 6.5-284 round with the 140-grain Hornady SP bullet seated so the base was flush with the base of the case neck had 30/1000-inch (0.75mm) jump to the rifling. He then re-cut the barrel shoulder, shank, and threads, so installing the barrel on the receiver would give correct headspace (6/1000-inch clearance with the go gauge). Finally, he installed the barrel on an action.
Then Christer and I cleaned and fouled the barrel, while working up a load that generated as close to 4100 BAR (about 59,500 psi) average pressure as we could get. We used Norma cases from the same production lot, sorted out pieces that were between 201.5 and 202.5 grains (+/-½-grain of average weight). We used Winchester Large Rifle primers sorted to +/- 0.0025-grain weight (yes, we used a four-digit scale to weigh hundreds of primers — remember, our goal was to minimize variables). And, we precisely weighed charges of Norma MRP (literally, to the individual granule tipping the scale to the final tenth-grain for the desired charge weight.
Christer noted that MRP was ideal for 6.5-284 loads with 140-grain bullets. He’d tested many propellants in that load combination; MRP was king. We carefully charged the cases using my swirl-charge method.
Once we found the precise tenth-grain-increment propellant charge needed to get an average pressure very close to 4100 BAR, we loaded up ten rounds as precisely as we could. Then we fired those at a specific cadence, allowing the barrel to cool for precisely three minutes between shots. We printed out each pressure curve.
Then, we carefully cleaned the barrel. I then hand-carried the barreled action back to the machine shop. The machinist removed the barrel and set it up to re-cut the chamber, for the 6.5/60 case. When he finished, by deliberate design, we had a situation where the base of the seated bullet in the 6.5/60 loads would be exactly the same distance from the pressure port in the barrel as it had been in the 6.5/284 loads.
With Norma’s system, the pressure measurement port is normally located about 40/1000-inch forward of the mouth of the case. For this testing, we cut the 6.5-284 chamber so the port was forward of the case mouth enough so that when we rechambered for the 6.5/60, with its 0.185-inch longer neck, the port was 40/1000-inch forward of the case mouth. So, in both rounds, bullet travel was identical when chamber pressure first hit the port.
Because the 6.5/60 case neck is slightly thicker than the 6.5-284 case neck is, the entire chamber behind the throat was re-cut. This eliminated any bias in chamber quality because both reamers were designed to give 3/1000-inch total annular neck-to-chamber clearance, with a seated bullet, and 15/1000-inch endwise clearance between end of case-neck and beginning of the chamber-to-throat transition.
The machinist then re-cut the barrel shank and threads, so the new chamber would headspace correctly on the same action. Of course he used a different bolt, one that had been modified to fit the 416 case rim.
So, both chambers used the same barrel and pressure port. And, we had the same throat and lead, and the same neck clearances in both chambers. And, bullet travel distance was identical, both to the pressure port and to the muzzle.
We used the same pressure measuring equipment on the same day with all environmental conditions as identical as possible for both tests. We used the same lot of primers, propellant, and bullets.
In other words, we actually tried to perform a scientific comparison, with only the chamber design differing from one test to the next.
In this aspect, I’ve ignored the 20 or so shots we fired while establishing and testing the 6.5-284 load. Those shots certainly had to create some small measure of bore damage, but the barrel was already broken in before that began, and bore-scope analysis showed no visible heat checking before or after our testing; so, it seems unlikely any change from firing about 20, 6.5-284 rounds could have altered the subsequent 6.5/60 test results measurably.
With the rechambering finished, we again cleaned the bore. Then we started working up a load for the 6.5/60 chamber. As anticipated, MRP was too fast to be ideal in the shorter and fatter chamber — I already knew that how a propellant burns in the case depends upon case design. So, MRP was not ideal in the 6.5/60, but use of any other propellant would have added another variable to the test. The only way to come close to comparing apples to apples was to use the same components.
When we reached 4100 BAR, the charge was significantly less than in the 6.5-284 load, and the case had considerable room for additional charge. Obviously, a slower propellant with similar energy and progressivity would have given higher velocity.
Regardless of that, we carefully loaded and fired ten rounds with the requisite charge. As with the 6.5-284, after each shot, we printed out the pressure curve — this was a weakness of the Oehler 41 system, it had no memory to retain pressure curves from each shot, either you printed out the pressure curve page or you permanently lost that data!
After the first curve printed out, Christer studied the resulting graph carefully. He compared it to the 6.5-284 curve.
Then, as additional curves finished printing after each additional shot, he laid the new printed sheet over the previous ones. After the third pressure curve printed out, he laid it on top of the first two and held those up to a bright light, so he could see through all three sheets and compare the curves.
He looked at it carefully, to verify that the machine had actually printed the new curves and not just reprinted the curve from the previous shot — each test is automatically assigned an incremental number. He then shook his head, looked through the three thin sheets again, turned to me, and fairly fulminated, “These are, by far, the most consistent pressure curves I have ever seen.”
This statement, coming from a man who had seen thousands of sets of such curves, gave me pause to ponder. While I had predicted improved ballistic uniformity, because of the superior case design, I had not expected it to be so much better that Christer would immediately notice it. This was a pleasant surprise indeed.
We continued shooting. Christer continued overlaying the pressure sheets. Twice more, in evident disbelief, he repeated his exclamation, “These are the most consistent pressure curves I have ever seen!” It was as if he were trying to convince himself that he was not seeing what he was seeing.
After the tenth shot, he handed me the stack of ten thin printer sheets, I carefully aligned those and held those up to the light, What I saw was one heavy line from start to finish of the pressure curve, any deviation was practically indistinguishable at that scale.
He then handed me the ten sheets from the 6.5-284 test. I aligned those and held those up to the light, I could see five or six separate curves in several places along the traces, and nowhere were the ten pressure curve traces coincident, other than where various curves happened to cross. Ignition delay varied, pressure rise varied, peak pressure varied, and muzzle pressure varied.
I asked Christer how the consistency of these 6.5-284 curves compared to typical pressure curves. He said, “The 6.5-284 usually does better than average, and this load did too. I used to think this was because MRP is such a great match to the 6.5-284 with 140s; and that, perhaps, the case size and that charge just happened to work well with the Winchester primer. Now, after seeing how well the even shorter and fatter 6.5/60 does, I am wondering if the fact that the 6.5-284 is a relatively short and fat case explains why it does better than average.”
Anyway, the difference between the two sets of pressure curves was startling to me too. I just did not have the experience to realize how exceptionally consistent the 6.5/60 curves were. However, as noted, I was quite pleased with this result.
The other pleasing result was that, despite having used an ideal propellant in the 6.5-284 and an obviously less than ideal propellant in the 6.5/60, and the 4% usable capacity deficit of the 6.5/60, the SMc chamber generated 40-fps more velocity at precisely the same pressure. That, is a substantial velocity difference.
So, Christer suggested we try Norma’s new slow propellant, Norma 217, developed for the 30-378 Weatherby Magnum. I said, sure. I asked what charge we should start at. Without thinking about it enough, perhaps because he was overworked by yours truly, Christer replied, “Doesn’t matter much, there is no way we can get enough 217 in the case to generate full chamber pressure in this comparatively small case.” (He meant that, compared to the 30-378 Weatherby Magnum, the 6.5/60 had significantly less capacity as a ratio of cross-sectional bore area to usable case volume.)
So, we charged a case with enough 217 to fill the neck about halfway, took that round to the lab, chambered it and fired it. Velocity exceeded 3450-fps, pressure far exceeded 78,000-psi (A fine proof load!), and the bolt was locked solid. Getting the stuck case out of the chamber, without destroying something, required removal of the barrel and the machine shop was long-since closed.
So, Christer got a lesson in internal ballistics with SMc cases, and we were through testing that day. As life would have it, we could not get back to 6.5/60 testing, so we have no idea how much velocity edge this round might have had over the 6.5-284, if we had tested it with a more appropriate propellant. Obviously, 217 would qualify as a good choice, if we’d have started with just a few grains less charge we might have learned that then and there!
Soon thereafter, when Norma standardized the 5/35 SMc and tested it at the CIP Lab, to establish CIP specifications, the results supported my belief that the pressure system Norma uses gives higher relative readings with any short-fat case and the SMc design results in a comparatively high pressure reading as the bullet clears the port.
The way the propellant burns in the SMc case results in a faster pressure rise with the same peak pressure, when compared to an otherwise similar case of similar capacity using a propellant of similar effective burn rate. With the Norma measurement system, this results in an inertial influence that biases the readings. Because of this, the SMc design shows higher peak pressure when the actual peak pressure is identical. CIP uses the conformal pressure system with drilled cases and a pressure transducer located about halfway along the case wall. This system minimizes inertial biases.
In the 5/35, the bias between the Norma system and the CIP system proved to be worth about 60 fps with most tested loads — when loaded to generate the same recorded peak pressure with both systems, the charge was significantly lower with the Norma system and velocity was about 60 fps less.
Therefore, a reasonable expectation is that the 6.5/60 would have generated about 40 fps more velocity than it did, if it had been loaded to the same actual peak chamber pressure as the 6.5-284 was. (The velocity difference would have been less than in the 5/35 because of the differences in relative bullet weights and muzzle velocities.) So, as a best guess, even with the wrong propellant in the 6.5/60, it still had a 95 fps velocity edge over the 6.5-284 — 15-fps deficit, from the capacity deficit; plus, 40-fps from the pressure deficit; plus, the measured 40-fps velocity advantage the test showed. Moreover, I suspect Norma 217 would have given at least another 25-fps. In the 6.5/60, the SMc design therefore seems to have a velocity edge of about 120 fps, which translates to an energy advantage of about 10%, at least a 5% velocity advantage, over traditional case designs. In typical rifle loads, 5% is about 125 fps.
So, the SMc testing proved what we wanted to prove: If the question is, is the SMc Design superior to standard chamber designs, the answer is and unequivocal yes, it is superior in every measure: velocity, consistency, barrel heating, and felt recoil. (The latter two advantages are the inevitable result of conversion of more of the propellant energy into bullet energy, as explained in the SMc Patents.)
The following day, we got started on a test to see what influences seating depth had on 308 Winchester loads using both naked and properly moly-plated bullets. For these tests, we grabbed a bunch of 308 Winchester cases that were otherwise finished, excepting the broaching of flash holes. We sorted those by weight and drilled the flash holes, to generate more precise flash-hole diameter, length, and entrance and exit characteristics. We used the same approach for a study of flash-hole diameter, which proved that, at least with the load combination we tested in the 308, flash-hole diameter made very little ballistic difference, so long as it was uniform from case to case.
For this testing, we carefully selected and prepped cases, as described below. We used 168-grain Sierra MatchKing bullets, precisely weighed Winchester Large Rifle Primers, and Norma-202 propellant, which has a very good burn rate for such a load. As I recall, we settled on 42 grains for testing of the naked bullets and adjusted the charge to 43.2 grains for testing with the moly-plated bullets, to give the same peak pressure as the naked-bullet loads. At any given overall length, and when the charge was adjusted to give the same peak pressure, the friction-proofed bullets averaged about 25-fps higher velocity. This was all as anticipated.
Generally, the results of that testing was about as expected, using 30/1000-inch bullet-to-rifling jump as the baseline, up to a point, seating the bullet either farther from or closer to the rifling tended to increase ballistic variation. Beginning about 10/1000-inch off the rifling, the more jump the bullet had, the lower the peak pressure was. But, at about 40- to 50-thousandths-inch of jump, progressively shorter loads began to generate progressively higher pressure.
The longer loads, where the bullet had little or no jump to the rifling, were expected to generate higher pressure, because the bullet would have to accelerate from a stop, therefore breaking free from the static friction in the case neck (static friction is always significantly higher thin dynamic friction is) at the same time the rifling was engraving into the bullet jacket. That is what happened. With less than about 10/1000-inch jump to the rifling, pressure tended to begin to increase with both the naked and friction-proofed bullets.
However, one test gave some interesting fodder for thought, see below.
In the progressively shorter loads, when bullet-to-rifling jump exceeded about 50/1000-inch, no further benefit from added bullet velocity at the onset of rifling engravement occurred. Decreasing load length beyond that point merely reduced propellant boiler room, with the expected outcome of increased peak pressure.
Also, as we expected, with both naked and friction-proofed bullets, shot-to-shot ballistic variation tended to increase as bullet-to-rifling jump deviated progressively farther from about 30/1000-inch. This correlation was rather weak for the progressively shorter loads but quite strong for the progressively longer loads, with bullets almost touching, touching, and driven progressively farther into the rifling (5-, 10-, 15-, and 20-thousandths-inch) showing progressively increasing and dramatic variation in both pressure and velocity.
The one perplexing result was the load with moly-plated bullets just touching the rifling. This combination generated a phenomenal 15% lower peak pressure than the next-lowest-pressure combination among the moly-plated load tests with bullets at -20, -15, -10, -5, 0, 10, 20, 30, 40, 50, and 60 thousandths-inch off the rifling. Not only that, but the muzzle velocity was higher than any other tested load, despite the total area under the pressure-time curve being significantly less! This result seems ballistically impossible, but it happened.
I can imagine two possible, if only partial, explanations. First, for some unknown reason, that load generated far less barrel heating; so more of the energy produced by the burning propellant was available to accelerate the bullet. Second, perhaps for some other unknown reason, it also, somehow, resulted in significantly more of the charge being trapped behind the case shoulder, thereby improving efficiency, because less unburned propellant was accelerated down the bore — less energy wasted accelerating unburned propellant, more energy available to accelerate the bullet. But, it is impossible to model any way that this factor alone could have made so much difference. This result had to have been from a combination of improved efficiency of the propellant burn and decreased loss to barrel heating. I just do not know how so much difference could happen, but it did.
This just goes to prove a ballistician friend’s comment about such things: “Every time I think I’ve figured something out in the ballistics lab, the next day I try to duplicate the results and discover I was confused.”
Norma afforded me a fantastic opportunity to spend time working in its loading room and ballistic laboratory; the chance to meet and work with some wonderful people; and, a great time moose hunting. Collectively, every aspect of that experience is part of a wonderful lifetime memory; individually, those experiences were each special to me.
What Christer and I learned include ballistics details that few others will ever know or learn, I fear. What Christer taught me about working in the lab and many other things that Norma had studied are experiences that added to my knowledge base.
My only regret is that I was not able to take my late wife with me, so she could visit the ancestral home of her grandparents. Of course, we planned to do that, some day, but some day never came for us. Having lost her in 2017, I am now destined to enter my sunset years with only my memories, so these special remembrances are extra special to me.