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By Kevin Newberry
Kevin continues his quest for ultimate accuracy using heavy .224 bullets and Norma 203B.
I say detour because there have been a few interesting developments since I wrote Phase I. Originally, I had planned to do this report in 3 phases, but it will conclude with Phase II with Phase III being left up to the individual handloader. I’m not trying to duck out on you guys and I will provide some useful information. A situation has arisen with my chronograph that I haven’t resolved, and it was a replacement for the original I bought in March of 2013. I have no fault with the manufacturer, so I won’t list them or the model, but I will say that their customer service is excellent. They replaced the first unit without question and have already committed to do the same again. In the interest of being fair to them, I want to be absolutely sure that there is a problem that isn’t the result of getting different velocity and statistics than from the original unit that stopped recording the majority of rounds in a ten-shot string. I am under no time constraint and their customer service technician is in complete agreement with this approach where if it does have to go back, he’ll essentially do the same in firing the same loads at different times and compare the results. Ambient light is definitely a factor, so I’ll mention that I constrain chronograph testing to where the sun is forty-five degrees or higher above the chronograph. Another factor is that it is spring here in the Heart-of-Texas where we collect the majority of our annual precipitation. So, during the past few range sessions it’s cloudy with no skyscreens mounted one minute where by the next string of fire the sun is out and the skyscreens are re-mounted. The given velocities are from the second chronograph.
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Immediately after writing the first segment, my shooting partner received the Hornady 9th edition load manual and they show 5.56mm NATO data for Reloader 15 and N203B. I won’t go in to great detail about the Hornady data except to say that the pressure Max. used is stated to be SAAMI spec while we know that 5.56mm NATO is loaded to and set by a C.I.P. spec just as Western states it at 62,350 PSI. The thing I noticed immediately is that the Max. Charges for N203B are only .1 grain higher than for Reloader 15. Honestly, this presented questions that made me question some of my statements in Phase I. It doesn’t mean that N203B isn’t a more refined version, and in this particular instance, the Reloader powder preceded the Norma. First there was N203, than later Bofors began selling a powder to Alliant we know as RL-15. Then came N203B while N203 was discontinued. So, if N203B is a refined version with greater care given in manufacturing and quality control, it certainly has a place in 5.56mm NATO handloads where ultimate accuracy with the Hornady 75 grain BTHP-Match w/c is the goal. And, let’s face it, these aren’t just your everyday combat type rounds.
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After Phase I also began investigating articles where comparisons were made in regard to pressure vs. charge-weight. Eventually, I came across a discussion where the powders were put to the test in a 62,000 PSI target cartridge, the 6.5 X 47mm Lapua loaded with the 130 grain Berger VLD. To achieve the maximum pressure of 62,000 PSI for the cartridge, the N203B loads required a higher charge, but only by .2 grains. The problem is, the test was strictly predictions from the QuickLoad Ballistics program. It is not unusual that the computer program differs from reality. Here’s what we know about N203B:
Norma 203B Chemistry
According to the Norma Reloading Handbook #1, Norma 203B has the following composition:Image may be NSFW.
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85% Nitrocellulose
7.5% Nitroglycerin
2.0% surface coating
4.6% Various chemicals
0.9% Water
3,957 J/g specific energy
890 g/l specific density
For comparison, the 7.5% NG component compares to 15% in Viht N500 series powders and 10% in Ramshot TAC / Big Game / Hunter.
We see that it is not a single-based extruded propellant, and it isn’t likely that you’ll find the exact chemical composition of Reloader 15. Not in my experience putting forth technical questions to Alliant; not quite as challenging as a powders exact chemistry. As far as the question of economy and using Graf & Sons current pricing as a guideline, the Vihta Vouri N100 series powders are priced at $35.99 vs. the $29.59 price for N203B where Norma obviously formulated it to compete with the Vihta Vouri “High Energy” N500 Series powders that sell for $40.99/Lb.
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So, most of our “detour” came from using lighter charge-weights: my shooting partner made loads at 2 different charge-weights of 23.5 grains and 24.5 grains while my loads were the aforementioned 25.0 grains. From the 16” barrel; using the Hornady “T2” bullet with an OACL of 2.248” charged with 23.5 grains of N203B, the load chronographed 2520 FPS. At 24.5 grains velocity was 2662 FPS 15’ from the muzzle. I can’t list the velocity at 25.0 grains because of questions about the accuracy of the data received. But, there were absolutely no signs of excess pressure and I would recommend a Start Charge for 5.56mm NATO at 24.5 grains and work up from there based on your barrel length, rifle, etc. That is only 88 FPS below the velocity goal of 2750 FPS from the 16” barrel. At this point I do not believe that powder compression will be a negative issue.
There is one other load recipe I did not mention, because assumptions are involved. It involves the load with the Hornady 75 grain A-Max in the Lyman 49th Edition. It is definitely a .223 REM. “Custom Long Throat” load (as prudently categorized in Western’s data) with an OACL of 2.390” that can not be used in AR rifles. It is also charged with Reloader 15 with Max. Pressure listed as 52,400 CUP, where 52,000 CUP equates to 62,000 PSI in most cases. And an assumption would have to be made about the required charge of N203B. To me, the most likely differences between the 2 powders in question would be bulk density, Nitroglycerin content, Surface coating and percentage of “Various Chemicals.” Without the exact chemical composition of RL 15, you would be assuming that the QuickLoad software had made an accurate analysis of the 2 powders. Until proven otherwise, I am not prepared to say that they are similar enough that slight differences in charge-weight, pressure and velocity that they simply vary by individual lot.
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In the final analysis, accuracy, I can tell you that I shoot the tightest groups possible while chronographing while I can not eliminate the consideration of a chronograph being in front of me, lingering in the back of my mind as I shoot. I apologize for the chrono issues, but comparing the velocities of the 2 loads made by my shooting partner at 23.5 and 24.5 grains of N203B, there was a gain of 142 FPS for the 1 grain increase in charge-weight. I think it’s fair to say that we can’t expect linear increases with charge-weight increases, especially not when approaching Max. Pressure levels. But, if my previous recording of 2662 FPS at 24.5 grains was in fact an accurate one, I should have been slightly above 2700 FPS with the 25.0 grain charge. Again, I believe it would be very prudent to use 24.5 grains of N203B vs. 25.0 grains for a 5.56mm Start Charge, or even less if that gives you greater confidence in safety. 10 rounds will easily tell you important facts concerning pressure from your individual rifle. Also, my shooting partner’s shooting abilities I consider equal to my own, though when it comes to splitting hairs, he wants to see what I can do with a group regardless of the number of rounds fired. His CRX-16 “Marksman” wears a Nikon P-223 3 -9 X 40mm scope with the zero-return function. On our last shoot he decided to do some experimenting to see if that particular function was reality or merely a sales feature. When he was convinced that it is indeed as accurate as advertised, he fired a 10 round group with my load at 25.0 grains of N203B. All 10 rounds were in the 1” bull at 100 yards.Image may be NSFW.
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As far as an ultra-accurate load I’m sure we’ll continue to experiment, but I did want to get back to you guys with some specifics regarding load data. For most loads we’ll probably continue to use TAC and AA 2520 simply because we’ve found no need to trickle powder charges. The chronograph anomalies are regrettable, but that’s from my rifle, not yours, anyway. Most of you will be chronographing. For those who won’t be, you should be able to get to 25.0 grains without signs of excessive pressure. In my opinion you will not be flirting with the pressure limit of 62,350 PSI/CIP while you may be flirting with gilt-edge accuracy. Knowing what a great group of people there are at Western Powder Company, and with the lack of data from Norma above 69 grain bullets, maybe we’ve helped give some data worthy of pressure testing that will be far more conclusive than my opinions alone. In past talks with Rob Behr, I believe they’re open to doing such tests.
Good shooting, Folks!
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Kevin Newberry
Kevin Newberry is a Texas-based gun writer and author. His book, Kilroy: Kilroy was Here, is available on Amazon.com in both paper and electronic versions. Image may be NSFW.
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