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Molon
31 March 2015, 10:07
Winchester Ranger 5.56mm 64 grain RA556B Ammunition

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Today, we have a wider selection of quality self-defense ammunition for our AR-15s to choose from than ever before. The construction and function of these modern self-defense loads is not limited by the archaic confines proffered by the Hague Conventions and far surpasses the consistency of terminal ballistic properties of “old school” loads such as M193 and M855.

There are two modern schools of thought regarding the selection of the type of projectile to use in a self-defense load; the first preferring a fragmenting, heavy (75-77 grain) OTM type bullet and the second opting for an expanding “blind-to-barriers” bullet. The top performers in the fragmenting, heavy OTM type category are Hornady’s 5.56mm 75 grain TAP T2, the Nosler 77 grain Custom Competition and the new Black Hills Ammunition load utilizing the Sierra 77 grain Tipped MatchKing.

A plethora of 5.56mm/223 Remington loads utilizing expanding barrier-blind projectiles have come to the market in the last several years. One of the top performing loads in this category is currently issued by the FBI; the Winchester Ranger 5.56mm 64 grain RA556B. Terminal ballistic testing conducted by Dr. G.K. Roberts has shown that this load has an average penetration depth of 17.1” in bare 10% ordnance gelatin with a recovered diameter of 0.46” (when fired from a 16" barrel.) After passing through an intermediate barrier of automobile safety glass, the load has an average penetration depth of 13.6” with a recovered diameter of 0.35” (again from a 16” barrel.)

The Winchester RA556B load is topped with the Nosler 64 grain Bonded Solid Base projectile. This bullet has a copper base that comprises almost one-third of the length of the projectile. Obviously, the lead core is bonded to the copper jacket. The bullet has a cannelure and a “Protected Point” design for reliable feeding in AR-15s





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Winchester’s RA556B ammunition is loaded in WCC 5.56mm brass that has the annealing iris still visible. The primers are crimped and sealed. The case mouth has a heavy collet crimp and “black Lucas” sealant. The cartridge is charged with “ball” powder.




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A ballistic table on the back of the RA556B ammunition box claims that this load has a muzzle velocity of 2935 FPS, but unfortunately there is no mention of the barrel length used for this figure. The standard barrel length for assessing the velocity of 5.56mm ammunition is a 20” barrel. A review of Winchester’s law enforcement ammunition catalog revealed that the above figure was indeed derived from a 20” barrel with a NATO chamber and a 1:7” twist.




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Speed is fine . . .

I chronographed the Winchester Ranger 5.56mm 64 grain RA556B ammunition from a semi-automatic AR-15 with a chrome-lined, NATO chambered 20” Colt M16A2 barrel with a 1:7” twist.




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Chronographing was conducted using an Oehler 35-P chronograph with “proof screen” technology. The Oehler 35P chronograph is actually two chronographs in one package that takes two separate chronograph readings for each shot and then has its onboard computer analyze the data to determine if there is any statistically significant difference between the two readings. If there is, the chronograph “flags” the shot to let you know that the data is invalid. There was no invalid data flagged during this testing.

The velocity stated below is the muzzle velocity as calculated from the instrumental velocity using Oehler’s Ballistic Explorer software program. The string of fire consisted of 10 rounds over the chronograph.




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Each round was single-loaded and cycled into the chamber from a magazine fitted with a single-load follower. The bolt locked-back after each shot allowing the chamber to cool in between each shot. This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Each new shot was fired in a consistent manner after hitting the bolt release. Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.




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Atmospheric conditions

Temperature: 76 degrees F
Humidity: 45%
Barometric pressure: 29.96 inches of Hg
Elevation: 950 feet above sea level


The muzzle velocity for the 10-shot string of the Winchester RA556B ammunition fired from the 20” Colt barrel was 2976 FPS with a standard deviation of 20 FPS and a coefficient of variation of 0.67%.

For those of you who might not be familiar with the coefficient of variation (CV), it is the standard deviation, divided by the mean (average) muzzle velocity and then multiplied by 100 and expressed as a percentage. It allows for the comparison of the uniformity of velocity between loads in different velocity spectrums; e.g. 77 grain loads running around 2,650 fps compared to 55 grain loads running around 3,250 fps.

For comparison, the mil-spec for M193 allows for a coefficient of variation of approximately 1.2%, while one of my best 77 grain OTM hand-loads, with a muzzle velocity of 2639 PFS and a standard deviation of 4 FPS, has a coefficient of variation of 0.15%.




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Accuracy is final . . .

I conducted an accuracy (technically, precision) evaluation of the Winchester Ranger 5.56mm 64 grain RA556B ammunition following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any group-reduction techniques (e.g. fliers, target movement, Butterfly Shots).

The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Also, a control group was fired from the test-rifle used in the evaluation using match-grade, hand-loaded ammunition; in order to demonstrate the capability of the barrel. Pictures of shot-groups are posted for documentation.

All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrel used in the evaluation was free-floated. The free-float handguards of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was attached to the objective-bell of the scope. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.




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The Wind Probe.

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The test vehicle for this evaluation was one of my semi-automatic precision AR-15s with a 20” stainless-steel Lothar Walther barrel. The barrel has a 223 Wylde chamber with a 1:8” twist. Prior to firing the Winchester RA556B ammunition, I fired a 10-shot control group using match-grade hand-loads topped with the Sierra 55 grain BlitzKing. That group had an extreme spread of 0.635”.




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Next, three 10-shot groups of the Winchester RA556B load were fired in a row with the resulting extreme spreads:

2.03”
1.77”
1.90”

for a 10-shot group average extreme spread of 1.90”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the 30-shot composite group was 0.66”.




The smallest 10-shot group . . .

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The 30-shot composite group . . .

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The graph below shows the trajectory of the Winchester RA556B load when using a 50 yard zero when fired from the 20” Colt barrel.




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Nosler claims that their 64 grain BSB bullet has a minimum velocity expansion threshold of 1600 FPS. Based on that figure, when fired from a 20” Colt barrel with a NATO chamber and a 1:7” twist, the RA556B load will expand out to a distance of approximately 410 yards.




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…..



A PRIMER ON THE MEAN RADIUS

The Mean radius is a method of measurement of the dispersion of shot-groups that takes into account every shot in the group. It provides a more useful analysis of the consistency of ammunition and firearms (accuracy/precision) than the commonly used method of extreme spread.

The typical method used to measure a group consists of measuring the distance between the centers of the two most outlying shots of a group. This would be the “extreme spread” of the group. We are essentially measuring the distance between the two worst shots of a group. Take a look at the two targets below.




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Most people would intuitively conclude that the second target shown is the “better” group. Measuring the two groups using the extreme spread method, we find that both groups measure 2.1”. Once again with the typical method of measuring groups we are measuring the distance between the two worst shots of the group. This method tells us nothing about the other eight shots in the group. So how can we quantitatively show that the second group is better than the first? (Yes, we could score the groups using “X-ring” count, but this does not give us any differential information about all those shots in the X-ring.) This is were the mean radius method comes in. It will give us that extra information we need to better analyze our groups, rifles and ammuntion. If I just reported the measurements of the two groups above using the extreme spread meathod, without a picture, you would assume that the two groups were very much the same. Using the mean radius method shows that the second group is much more consistent. It has a mean radius of 0.43” compared to 0.78” for the first group.

Mean radius as defined in Hatcher's Notebook “is the average distance of all the shots from the center of the group. It is usually about one third the group diameter (extreme spread)” for 10-shot groups.

To obtain the mean radius of a shot group, measure the heights of all shots above an arbitrarily chosen horizontal line. Average these measurements. The result is the height of the center of the group above the chosen line. Then in the same way get the horizontal distance of the center from some vertical line, such as for instance, the left edge of the target. These two measurements will locate the group center.

Now measure the distance of each shot from this center. The average of these measures is the mean radius.

Once you get the hang of measuring groups using the mean radius it becomes very simple to do. While being very simple to do, it is also very time consuming. Modern software programs such as RSI Shooting Lab make determining the mean radius a snap.

The picture below is a screen snapshot from RSI Shooting Lab. The red cross is the center of the group (a little high and right of the aiming point). The long red line shows the two shots forming the extreme spread or group size. The yellow line from the red cross to one of the shots is a radius. Measure all the radii and take the average to obtain the mean radius.




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Mean Radius Demonstration

Let’s say you fired a 5-shot group from 100 yards and the resulting target looks like this. (The X-ring measures 1.5” and the 10-ring measures 3.5”.)




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The extreme spread of the group measures 2.83”, but we want to find the mean radius (or average group radius.) In order to find the mean radius we must first find the center of the group. By “eye-balling” the target most people would see that the group is centered to the left of the “X-ring” and probably a little high, but we need to find the exact location of the center of the group.

Locating the Center of the Group

The first step in finding the center of the group is to find the lowest shot of the group and draw a horizontal line through the center of that shot.




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Next, find the left-most shot of the group and draw a vertical line through the center of that shot.




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Now measure the distance from the horizontal line to the other four shots of the group that are above that line. Add those numbers together and divide by the total number of shots in the group (5).




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2.50” + 1.03” + 2.01” + 1.30” = 6.84”

Divide by 5 to get 1.37”. This number is the elevation component of the center of the group.

Next we need to find the windage component of the center of the group. From the vertical line, measure the distance to the other four shots of the group that are to the right of the line. Add those numbers together and again divide by the total number of shots in the group (5).




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1.76” + 2.54” + 0.45” + 1.19” = 5.94”

Divide by 5 to get 1.19” This is the windage component of the center of the group.

Finding the windage and elevation components of the center of the group is the most difficult part of this process. Once that is done the rest of the process is a piece of cake.

Using the windage and elevation components, locate the position on the target that is 1.37” (elevation component) above the horizontal line and 1.19” (windage component) to the right of the vertical line. This location is the center of the group!




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Determining the Mean Radius

Now that we have located the position of the center of the group, the first step in determining the mean radius is to measure the distance from the center of the group to the center of one of the shots. This line is a single “radius”.




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Now measure the distance from the center of the group to the center of each of the rest of the shots in the group. Add the measurements of all the radii together and then divide by the total number of shots in the group (5).




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0.85” + 1.35” + 1.38” + 0.84” + 1.61” = 6.03”

Divide by 5 to get 1.21”. This is the mean radius (or average group radius) of the group!

Using the mean radius measurement to scribe a circle around the center of the group gives you a graphic representation of the mean radius. This shows the average accuracy of all the shots in the group. This demonstrates why the mean radius is much more useful than the extreme spread in evaluating the accuracy of our rifles and ammunition.




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The table below will give you an idea of the relationship between the mean radius and extreme spread for 10-shot groups.




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toolboxluis00200
31 March 2015, 10:53
good review very detail

DutyUse
31 March 2015, 11:55
Wow, extremely well done and documented review!

When I do any in the future I'll look to this as a reference standard


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