BIG Freakin’ Cartridge Test 012: RUAG SS109 (M855 Equivalent) 5.56mm NATO, 16″ and 20″ Barrels

    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.

    Continuing on from the last installment, we are now looking at the velocity test results for the 20″ barrel (more on the 16″ later).

    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. It needs to be noted that for all 16″ barrel testing, a cooling time of 10 seconds was used instead of 30, as it was becoming obvious that the additional 20 seconds were unnecessary. In the future, 10 seconds will be used for all barrel lengths.

    The chronograph results for the 20″ FN chrome-lined CHF barrel are as follows (Shot #, followed by muzzle velocity in ft/s):

    1. 3,095

    2. 3,118

    3. 3,078

    4. 3,065

    5. 3,094

    6. 3,077

    7. 3,126

    8. 3,094

    9. 3,080

    10. 3,115


    Which gave us the following figures:

    Min: 3,065

    Max: 3,126

    Avg: 3,094

    Standard Deviation: 20

    Extreme Spread (highest minus lowest): 61


    And the chronograph results for the 16.1″ Colt chrome-lined cut rifled barrel (Shot #, followed by muzzle velocity in ft/s):


    1. 2,893

    2. 2,936

    3. 2,918

    4. 2,955

    5. 2,958

    6. 2,940

    7. 2,968

    8. 2,970

    9. 2,996

    10. 2,949


    Which gave:

    Min: 2,893

    Max: 2,996

    Avg: 2,948

    SD: 28.8

    ES: 103


    Once again, the 20″ barrel proved more consistent (somewhat) than the 14.5″ barrel, but interestingly the 16.1″ barrel was less consistent. This does mean that, for all 6 rounds tested so far, the 20″ barrel has in every case produced more consistent numbers than the 14.5″. However, in some cases, this difference has not been very massive, and perhaps more interestingly the 16.1″ barrel has not always been in-between the two, sometimes (as in this case), being significantly less consistent than either.

    EDIT: RUAG International Sales Director Bert Roethlisberger reached out to TFB to help us understand the history of Lot T-17-001, and how it could produce such lackluster results. Bert’s comments are below:

    Bert here from RUAG Ammotec in Switzerland. I have read your test report with interest for the 5.56mm SS109 which was produced by us, RUAG Ammotec in Switzerland and would like to comment as follows.

    • As a norm we produce the 5.56mm SS109 NATO cartridge only for Military customers and never for civilian/commercial use.
    • The cartridges you were testing came from Lot # T-17-001 which was produced early last year for one of our military customer. As is SOP we continuously check the ammo for pressure, velocity and accuracy during the manufacturing process. About once every hour 50 rounds are pulled from the line and send to the test lab. During one of those tests variations in the loads was discovered and also the accuracy, by some samples taken, showed upper limit deviations and some even fell just out of specs.  Affected was also the velocity in some which showed greater than usual variations.
    • Based on those production test results our Q-team decided to stamp this Lot as “failed”, not for sale to the customer and it was pulled out.
    • We put approx. 550’000 rounds (Lot # T-17-001) in our warehouse and later on offered it to several commercial dealers as a one off special fire sale for anybody who wanted a good deal on 5.56mm ammo for backyard plinking.  This was made clear to the US dealer who finally purchased this Lot at a very good price.
    • This SS109 ammo was NEVER meant to be used for any accuracy testing but exclusively for plinking.  I like to stress again that it was ammo which failed our stringent quality requirements and therefore was NOT delivered to our Military customer.
    • RUAG Ammotec prides itself as being the manufacturer of high quality premium ammunition and we would never deliver inferior quality ammo to any customer unless as it is the case here it is made clear for what purpose this ammo should be used.”

    Reject lots are just a fact of life for ammunition production, and this ammunition is often released onto the commercial market as surplus. It’s certainly interesting to see how far “factory seconds” can deviate from what we expect of the real deal, though!

    Nathaniel F

    Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. He can be reached via email at [email protected]