Had the opportunity to pull apart a SIG M400 SRP - 16" 1/7. Interesting aspects - I was really surprised to see such a small gas port. I dropped gauge pins in the port and it appears to be .059" port.
My .0595" pin would not go in (barely) but the .055 pin dropped right in. I'm guessing a 1.5mm port or .0590. The other interesting aspect was that the barrel extension had two holes machined through the sides. One was at 8 o'clock and the other was 180 deg opposite at 2 o'clock. The 2 o'clock hole was plugged with a pin and the other hole was open.
Thoughts?
I'm guessing it was for tooling that installs the extensions - but that's just a guess.
I test fired it after reassmbly (hand guard / gas block / muzzle device upgrade) and it was a nice soft smooth shooting rifle. (M855) It was fired on a different lower with an H2 buffer and a Springco Blue.
Sweet upper.
FWIWSIG M400 SRP Bbl Ext.jpg
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