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

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:

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

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