After roughly 5,000 rounds, mostly suppressed, on my 16.1" DDM4 middy w/CHF Chrome-lined .gov profile barrel...I tore it down a bit...
-the gas tube "mushroom" measures 0.174". The new replacement is 0.18". At 0.174", the "mushroom" barely snags a fingernail. Wear was pretty even, with very slight bias to one side covering a distance of maybe 2 hours on a clock-face. Very very subtle bias.
-After roughly 2500 rounds (mostly suppressed) on my Azimuth QPQ carrier, the gas-rings showed zero wear to the "aspect" of the ring, ie. no material was missing from oscillating within the carrier, however, compared to new Colt mil-spec rings, they had "compressed" by roughly 0.005" when measured in full diameter once removed from the bolt.
-The gas port was spec'ed at 0.073" to me by DD, however, I think +- .001" is surely within spec. Pin gauges show it to be between 0.0735" and 0.0745" (my 0.074 gauge has not arrived yet).
-Within the last several hundred rounds, I fired a <1.5 MOA 10-shot group with this rifle using 75gr Gold Dot ammunition and a 4x optic at 100 yards.
-I have used so many buffer extractor and ejector spring combo's that I have nothing to report, here.
-The Surefire 556-212 has suffered 1 baffle strike, affecting several baffles and the end-cap, very minor. I do not know what caused it, and aside from visual, there are no symptoms of it happening either when it occurred, or later.
-The Surefire 556-212a muzzle-device has eroded between the tines so that the once "rounded scoops" nearest the end of the muzzle device now resemble garden spades. This erosion is MUCH less than I noted on my Noveske, with its 14.5" barrel after similar round-count. That 1.6" of barrel made a huge difference, here.
-I have no way to measure rifling, but I can still clearly see where each land begins, although they don't begin as "crisply" as they once did.
-If there is anything else you want mic'ed or gauged, let me know before I put it back together.
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Originally Posted by Eurodriver
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