View Full Version : M193 & PMC Bronze 5 shot Groups
Went to the Range today, to shoot some 5 shot groups @ 100 Yards with American Eagle XM193 and PMC Bronze 55gr FMJ.
Groups were shot off a Sandbag on the bench and utilized a Badger Bone under the Pistol Grip.
MSTN Upper (16" SS Noveske 1:8" 3 groove ILGS)
Trijicon 1-4x w/ Red Triangle on ADM Recon QD Mount (a really awesome member on here graciously let me borrow it so I can T&E it)
Geissele Super Tricon
Geissele Mk4 M-LOK
SLR Sentry 7 Melonited Set Screw Adjustable Gas Block
Vltor A5 System w/ Green Spring and A5H2 Buffer
87 Degrees Fahrenheit
1-3mph Winds from 1-2 o'clock
68% Humidity
29.85 Barometric Pressure
392ft Elevation
Shooting these groups via the 4x Triji sure made things interesting... guess I was too spoiled, always used Higher Powered Glass (min. 10x) when trying to shoot Groups ;)
I really do like the Triji 1-4x... it's my first time ever actually utilizing one on a Rifle.
Measuring was done via a Vernier Caliper and I just measured the distance in inches between the two farthest rounds from the 5 shot groups... I know not everyone does it that way or maybe it's not super official, but I don't have OnTargetCalc and I've always done it this way, right, wrong, or indifferent.
http://i102.photobucket.com/albums/m119/HD1911/Mobile%20Uploads/60D23BFF-D4DD-464D-973D-15D874A03E6E_zpsiulp6d6z.jpg
http://i102.photobucket.com/albums/m119/HD1911/Mobile%20Uploads/36064C0D-5C9A-4491-9824-F05285AB6D3E_zps0xge6lst.jpg
Good post, and good shooting. It's great to see more than one group. I once went to the range, put 5 shots of PMC over a chronograph, and thought people who couldn't shoot it well were giving the stuff a bad name. At a later date I chronographed 10 more shots and found some huge deviations. Further testing reinforced my findings. Since then, when I'm trying ammo I try to shoot several groups, preferably on at least two range trips.
Thank you, sir. I'd like to get out there again and do it here soon, just to see if I can repeat or improve compared to today's outing. Might do it next time with some more magnification.
I'd love to chrono em' some time. By chance, do You remember at all what kind of speed the PMC was doin'?
I can run OnTarget for you on that picture - what's the diameter of the biggest target circle from edge to edge?
Thank you, sir. I'd like to get out there again and do it here soon, just to see if I can repeat or improve compared to today's outing. Might do it next time with some more magnification.
I'd love to chrono em' some time. By chance, do You remember at all what kind of speed the PMC was doin'?
I'll check my notes tonight, but I'm tempted to say 2910ish from a 16" barrel.
I can run OnTarget for you on that picture - what's the diameter of the biggest target circle from edge to edge?
6" exactly, to the outermost neon yellow edge. Thank you very much.
I'll check my notes tonight, but I'm tempted to say 2910ish from a 16" barrel.
Awesome, thanks.
6" exactly, to the outermost neon yellow edge. Thank you very much.
http://i.imgur.com/cXaAJCf.jpg
^^^ Thanks!
So is "Max" the one I need to be concerned with? It looks pretty close to what my measurements were... within a tenth or two anyways.
What is the "ATC"?
"Max" is extreme spread, the biggest distance between the center of any two rounds.
"ATC" is average to center or average mean radius. It calculates the exact center of the group then takes the average (mean) distance of each shot to the center. If you look at Jack's recent thread (https://www.m4carbine.net/showthread.php?170763-Let-s-Talk-About-quot-Accuracy-quot), he goes over it in more detail.
ATC is a better indicator of the precision of your group, but requires a lot of math if you're doing it by hand. Extreme spread is a lot easier to measure and it's the yardstick of accuracy for 99% of shooters on the Internet rather than ATC.
If you compare your bottom middle and bottom left M193 groups, you'll notice that while the bottom left is better in extreme spread, the bottom middle is better in ATC. You'll also note that the bottom left group is more spread apart while the bottom middle has a tight group with one "flyer". ATC takes into account a tight group while extreme spread only cares about the two furthest shots in a group.
On a side note, the term "average mean radius" is kind of redundant, isn't it?
Copy that. Good info. Appreciate it.
Here are my Chronograph results.
Setting: 45 Degrees F*, 1600 Feet above sea level, 28 November 2014.
Remington 700 223 5r 24" barrel (approx 200 rounds through the rifle)-
Average Velocity: 3068
Extreme Spread: 131 FPS
Standard Deviation: 48 FPS
S&W M&P15 16" Barrel/Blue Sprinco/H2 Buffer (approx 2500 rounds through the carbine)-
Average Velocity:2916 FPS
Extreme Spread: 42 FPS
Standard Deviation:11.61 FPS
I'll note that when shooting PMC Bronze, if I'm paying attention I'll sometimes feel some rounds having a little more or less kick that the rest of them.
What is the "ATC"?
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.
https://www.box.com/shared/static/05kmhft6cvk0w96q771e.jpg
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.
https://www.box.com/shared/static/e5h310mx2lw65cuuwrfk.jpg
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”.)
https://www.box.com/shared/static/pn6jf1qeuywk5a42jzcz.jpg
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.
https://www.box.com/shared/static/hg77du60v6jwj6qnhsd2.jpg
Next, find the left-most shot of the group and draw a vertical line through the center of that shot.
https://www.box.com/shared/static/qyqecvzn8slmls96199f.jpg
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).
https://www.box.com/shared/static/k0uuxzzb1weo3ppgluz7.jpg
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).
https://www.box.com/shared/static/ncg6hkbmcv1kyyvtdua1.jpg
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!
https://www.box.com/shared/static/46cr6kei23k2npjbwopy.jpg
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”.
https://www.box.com/shared/static/vm7k0jzt5h941pfldlhj.jpg
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).
https://www.box.com/shared/static/lv461k9kjilx3jndshs4.jpg
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.
https://www.box.com/shared/static/g1480t5ca47zrae1du8i.jpg
The table below will give you an idea of the relationship between the mean radius and extreme spread for 10-shot groups.
http://www.box.net/shared/static/e4ckmi2y36.jpg
....
No surprise here... Basic M193 and PMC are ≈2moa ammo.
Not really too disappointing for bulk ammo, esp if you can get it on sale. Almost all the people I see shooting it are doing is hitting full size steel targets within 200 yards. It works for that. And the PMC brass actually has been decent in my opinion. When I see my non-reloader friends shooting PMC, it makes me happy.
I don't expect a lot of precision out of the PMC Bronze, but it is good and clean for plinking fodder. I have had some pretty good luck with the Federal American Eagle ammo. Not much more than the PMC, and a tad more accurate in my M&P.
I picked up some of the Winchester 5.56, in 55 grain. Going in the morning to shoot some of that, and some of the Federal 5.56 black box.
Molon: Awesome write up! Really appreciate!
Here's a nice little 5 Shot Group w/ PMC Bronze via T2 Micro @ 50M, just confirming where it Lands on Target w/ my Mk262 Zero... first and only group, just for funsies:
http://i102.photobucket.com/albums/m119/HD1911/Mobile%20Uploads/0547C379-9910-422D-8E6D-FCEF2C8922B7_zpsa64jfam1.jpg
All I was really getting at with this thread, is that for Most Practical Intents and Purposes, this kind of Ammo does quite well, in a Training or Critter-Gittin' environment, considering how affordable this stuff is.
I was really tickled pink one time with PMC Bronze because we were at the range, at night time, and no one could see the Steel Plates past 200 Yards... So I picked up my brother's BCM SS410 16" Factory Upper equipped w/ a NF 2.5-10x42 (zero'd @ 100y w/ Mk262) and was able to actually just barely make out the Steel Plate @ 300y... all I had left on hand for shoot-able ammo was PMC Bronze... and every single round I shot smacked that Steel every daggum time, I could not miss! Strong or Support Side, Benchrest or Improvised, I was killin' that plate. That honestly made me realize, that for Range Work and Fun Stuff, I no longer need to shoot Only High Quality/Match Ammo, even in a Semi-Precision/Practical Steel Plate role (out to a certain distance obviously)
Sorry to bore you guys to death on Independence Day!!!
The contributions in this Thread are much appreciated!!!
Merica'!!!
I evaluated the accuracy (technically, the precision) of the PMC Bronze 55 grain FMJ ammunition using my 20” stainless-steel Lothar-Walther barreled AR-15. This barrel has a 223 Wylde chamber with a 1:8” twist.
Three 10-shot groups fired in a row from the bench at a distance of 100 yards had the following extreme spreads:
2.22”
1.82”
2.15”
for a 10-shot average extreme spread of 2.06”. The 30-shot composite group had a mean radius of 0.72”.
Unfortunately, my cocker spaniel chewed-up my chronograph data for this load.https://app.box.com/shared/static/8xqhq6fzplm5ts9vnn02xms3lwn2jl1x.gif
The smallest 10-shot group . . .
https://app.box.com/shared/static/2af11wqqvyz7sxsl3tpoulg5hqyqs1ws.jpg
The guilty canine . . .
https://app.box.com/shared/static/pfefa4ta27.jpg
…..
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