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BIG Freakin’ Cartridge Test 011: RUAG SS109 (M855 Equivalent) 5.56mm NATO, 14.5″ Barrel, and Accuracy

This article was originally posted on Thefirearmblog.com

Next up for the Big Freakin’ Cartridge Test is RUAG Ammotec’s version of the NATO-standard SS109 round (equivalent to US M855). I believe the ammunition I tested may have been made in RUAG’s facility in Thun, Switzerland, although I have not confirmed that. The test procedure was as follows:

  1. Condition ammunition to 70 °F +/- 5 degrees for at least 1 hr (in practice ammunition was always conditioned overnight).
  2. Mount chronograph to barrel or rail.
  3. Record the temperature in the conditioned container before each string.
  4. Withdraw one round of ammunition from the cooler.
  5. Load and immediately fire the round.
  6. Cool chamber back to ambient conditions for 30 seconds
  7. Repeat steps 3 through 6 nine more times.

This procedure was followed for 14.5″, 16.1″, and 20″ barrel length velocity tests. To measure velocity, a Magnetospeed V3 chronograph was used attached to the barrels of the 16.1″ and 20″ uppers, and the rail of the 14.5″ upper. In addition, three 10 shot groups were shot for each round through my Criterion 14.5″ chrome-lined 1:8 twist hybrid contour midlength barrel in .223 Wylde, to determine accuracy. These targets were then analyzed using OnTarget analysis software.

The chronograph results for the 14.5″ barrel are as follows (Shot #, followed by muzzle velocity in ft/s):

1. 2,857

2. 2,879

3. 2,904

4. 2,944

5. 2,906

6. 2,913

7. 2,918

8. 2,923

9. 2,923

10. 2,929

Which gave us the following figures:

Min: 2,857

Max: 2,944

Avg: 2,909

Standard Deviation: 25.2

Extreme Spread (highest minus lowest): 87

Being RUAG ammunition, I expected very good accuracy. What I got was, well…

What on earth.

It was around about the time I looked at the RUAG targets that I began to appreciate the value of shooting 3 10-shot groups, instead of just one. Any one of these groups would give someone a significant amount of pause – they certainly did for me. I had many doubts about these results. Surely I must have gooned up, been lazy in my marksmanship, or had some other unrecognized problem. Yet, with three groups, all consistently…well, inconsistent, it’s difficult to convince myself of any of those things.

For the record, the results were an average (of all 3 groups) extreme spread of 8.434 MOA, with an average mean radius of 2.371 MOA. This is by far the worst result we have found so far in a BFCT evaluation. Compared to the lackluster results we got with the Golden Tiger, the RUAG is 71% bigger in extreme spread, and 54% bigger in mean radius.

Oddly, even with these abysmal accuracy results, the consistency of the velocity for the RUAG wasn’t so bad, suggesting that there is some inconsistency elsewhere in the ammunition (such as the bullet). In addition, the average muzzle velocity was very close to what we’d expect for SS109/M855 from this barrel length, at 2,909 ft/s.

16.1″ and 20″ velocity results will follow tomorrow.

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