Matthew Cameron does some testing –
A question that occurs with regularity on internet forums is whether 5.56x45 NATO ammunition (the military version of the .223) can be fired in sporting .223 chambers and vice versa. (Ed: see the “Ask the Experts” column in our last issue, #138).
Both rounds became popular because of cheap surplus military brass and the many commercial rifles available, making the .223 the most reloaded cartridge in the Western World.
The highest velocity BM 2 load utilised 50 grain Nosler solid-base projectiles.
The reason for the confusion however, is that the chamber dimensions have changed since the 5.56x45 was first adopted, and the current military loading uses a longer, heavier projectile than the original. While the case dimensions are very similar, the two rounds differ in both pressure and chamber shape; the military round is proofed to 60,000 CUP while its civilian counterpart stops at 52,000 CUP. Accordingly the military brass is thicker, thus reducing the powder capacity. Reloaders should be aware of this factor.
Typically the throat dimension in a .223 chamber is 0.085 inches, while in the 5.56mm chamber the throat is 0.162 inches. Thus .223 Remington ammunition may be safely fired in a 5.56 chambered rifle; however, firing 5.56 ammunition in a .223 commercial rifle may produce excessive pressure due to the shorter throat, and the projectile being jammed in the lands.
Note that SAAMI (Small Arms & Ammunition Manufacturers Institute) considers that firing 5.56 ammunition in a .223 chamber is unsafe.
THE RIGHT TWIST?
The change in projectile weight meant that the barrel’s twist has also altered. Originally rifles were produced with 1:14” twist rifling, quickly changed to 1:12” to stabilize the 55 grain military projectile, and then to 1:7” to handle the new, heavier 62 grain military projectile.
The test rifle was a standard Howa Model 1500 equipped with a Sightron 3.5x10 scope – an accurate rig right out of the box.
Rifling twist is something to consider when you purchase a rifle and may have a large bearing on the projectiles you use if you want accuracy rather than velocity. This is an often overlooked factor and in extreme examples, with the wrong twist, it may be difficult to even get projectiles to print on the target at 100 yards. Choosing the correct twist is particularly important if you are only going to use commercial ammunition and not reload.
Most rifles firing .224” calibre 55 grain projectiles will have a twist rate of between 1:12” to perhaps a maximum of 1:14”, depending on the manufacturer, but when you increase projectile weight into the 60 grains and above range you need a faster twist to stabilize them. While the faster twist barrels will normally shoot lighter projectiles accurately, there are limits; eventually the rotational force may literally tear some lighter projectiles apart, so research both rifle and proposed projectile before you buy!
Neither .223 rifles nor cartridges are mentioned in my 1964 issue of Gun Digest, but there are cartridges listed in the 1966 issue loaded with 55 grain soft point projectiles. In the same issue some US rifle manufacturers are already chambering for the cartridge, including the Colt AR 15, Remington 760 Gamemaster, Coltsman Standard and Custom rifle, and the Remington 40XB target rifle. None of the European rifles listed are chambered for the .223. The 1970 issue of the Shooters Bible shows Remington cartridges loaded with either a 55 grain PSP or HP design, and Peters listed a 55 grain soft point.
When rifles chambered for the .223 became available in New Zealand some of the first to use them were the professional cullers or pest controllers. There was a slight increase in range over the standard .222 Remington and the cheaper brass made the round an attractive proposition. Likewise in Aussie it was the professional kangaroo shooters who went for the .223 first. Perhaps the words of one long time shooter summed the situation up best.
“Like most professional shooters I started using a .222 Sako with 50 grain bullets; when AR 2207 powder became available I used that with magnum primers, they just seemed to produce a better cartridge. The .223 was the next logical step as the brass was cheaper. I’m still using the combination today. I tried the 55 grain bullets but the 50 grain is a little faster and a bit more accurate. Most professionals continue to use the .223 because of the cheap brass.”
THE .223 TODAY
When the opportunity arose to test some of the new ADI .223 brass I quickly agreed. The brass comes in lots of 100 in the inevitable plastic bag, and is made to exacting military specifications. Certainly most 5.56x45 NATO brass is thicker than the commercial .223 brass, after all it is loaded to higher pressures. I compared nine cases each of ADI and commercial brass, selected at random. The ADI brass was an average of 4.9 grains heavier and the necks were .001” thicker. Unlike their commercial counterparts the ADI cases still showed where the necks had received a final annealing, usually this is polished out in commercial brass. The cases bore the ADI head stamp and the figures 09.
I ran each lubricated case through the reloading die to ensure perfectly round necks. Usually it is necessary to chamfer new case necks to make projectile seating easier, but this was not necessary with the ADI cases as the insides of the necks were chamfered already.
There are a couple of other tests that indicate good quality brass. The first is to ascertain how much brass swarf is removed when you attempt to ream the primer pocket inside the case; usually there’s some residue from the punch. With this ADI brass I simply couldn’t find any, and after trying a dozen cases at random I abandoned the idea.
The second test involves centred flash holes in the primer pockets. In the first 100 cases I could not find a single unit with an off-centre flash hole. The third test is to see how much brass is removed when you square up the primer pocket with a uniforming tool; again I abandoned the idea as the amount of brass shaving was insignificant. In terms of quality this brass passed with flying colours – not surprising as ADI has made .223 brass for many years, the output in the tens of millions.
It was time to get down to the business of loading some cases and assessing the results. The rifle I used was a standard Howa 1500 with some 200 rounds through the barrel, equipped with a Sightron 3.5x10 scope. The rifle was shot at 100 yard targets, off a Harris bipod and rear sandbag for maximum stability.
The 55 grain soft-point loads. Note the annealing marks around the necks of these military cases, which are always polished off in the commercial rounds.
To provide a reasonable spread, initially I chose three different weights of projectiles and three different ADI powders. All the loads were taken from the 5th Edition of the ADI Handloaders’ Guide and none exceeded the published maximums.
I matched the 40 grain Nosler Ballistic Tips with AR 2206H powder, the 50 grain Nosler Solid Base projectiles with BM 2 (Bench Mark) powder, and lastly the 55 grain soft-points with AR 2208 powder. Remington 6-1/2 small rifle primers provided the ignition for each load. The top load in each case was the maximum specified in the ADI Guide. Load densities were very close to 100%, and two of the top loads were compressed.
I shot the initial test loads under excellent conditions, just a whisker of breeze and in bright sunlight, the temperature a comfortable 27 degrees C.
The 40 grain Noslers and AR 2206H powder produced the most consistent three-shot groups, the largest being 0.88 inches for an average of 0.72 inches for four groups; however the top average velocity was 325fps below the book maximum.
AR 2207 provided excellent results with 52 grain Berger hollow-points.
The Nosler 50 grain Solid Base projectiles and BM 2 Powder were a little more erratic in group size but still averaged an inch with the top load producing a 0.63 inch group. Velocity was much closer to the book figure of 3395fps with an average of 3318 fps.
The last load of 55 grain soft-points and AR 2208 powder was also somewhat erratic in terms of group size although they averaged an inch; velocity was also down from the top figure of 3385 fps, at 3084 fps.
A good group shot with the maximum BM 2 load.
Overall the initial groups for the three projectiles and powders averaged an inch or less, which to me is very acceptable.
Comparing all the initial figures it was obvious that this rifle preferred the top BM 2 load and the 50 grain Nosler Solid Base projectiles. There were however two other options that I considered worth pursuing. I had some 52 grain Berger hollow-point projectiles available, and since BM 8208 is close to BM 2 I decided to try this combination.
The maximum load for 53 grain projectiles on the ADI website was 25.4 grains of BM 8208. I made up four different loads of three cartridges each, increasing a 1/2 grain of powder at a time, the lowest load being 23.9 grains. It would be interesting to see how this compared with the BM 2 load in both velocity and group size.
The best of the 2206H loads.
The results turned out to be a bit of a mixed bag, the top load of 25.4 grains averaged 3099fps, well down on the maximum of 3310 fps. The best three shot group was 0.50 of an inch with the 24.4 grain load, and the largest 1.27 inches for the top load. Overall the group average was 0.775 inches.
In addition when the overall results were compared AR 2206H and the Nosler 40 grain Ballistic Tips provided the best accuracy. The four groups averaged 0.72 inches, with the best group at 0.55 inches. It was worth trying to see if this carried over to the 55 grain soft-points. The maximum load in the ADI Guide is 26 grains and the starting load 25 grains; this provided three loads increasing at a 1/2 grain per load. Once again three cartridges were loaded with each powder charge. Similar to the previous results the average velocity was 3105fps for the top load of 26 grains against the book maximum of 3315fps. Groups with this load averaged 1.55 inches. The smallest group with the middle charged weight was 1.16 inches.
I was interested to note that the best overall results were achieved with the fastest powder of the three I’d chosen, Bench Mark 2. There were other possibilities however in relation to loads using AR 2207, BM 1 and AR 2219, all with faster burn rates than BM 2. I shot all of these loads using the Berger 52 grain hollow-points. AR 2219 powder was matched with Federal small rifle bench rest primers, the starting load 22 grains plus three increments of a 1/2 grain each, to a book maximum of 23.5 grains. Again the results were somewhat erratic; the maximum charge only produced 2897fps and a group size of 0.88 inches.
BM1 powder coupled with the 52 grain Berger projectiles and CCI magnum primers produced similar results, the maximum charge of 23 grains averaged 2885fps, and a 1.22 inch group. The last groups shot with AR 2207, CCI 450 magnum primers and the 52 grain Bergers provided much better results. While the velocity was down a little off the book figures this load did produce a maximum of 2984fps. The grouping was consistent and by far the best overall, averaging, for the four different loads, 0.66 inches with the best at 0.45 inches. The second best set of numbers were achieved with BM 2 powder and 50 grain Nosler Solid Base projectiles. The overall group was 1.00 inch with a top velocity of 3318fps – the highest velocity of all the groups. I would prefer to have shot this load with the 50 grain Nosler solid bases to see what it might produce, but time did not permit. Bottom line: This ADI brass is up there with the very best – in my testing it was faultless.