I just built one that works with supersonic suppressed, supersonic unsuppressed, and subsonic suppressed.
The secrecy sauce has 3 components:
1) Gas port drilled out to 0.125” (i.e. max size a ~$60 at a gunsmith), and;
2) Installing and properly aligning a Superlative Arms clamp-on adjustable gas block ($90).
3) A yellow Sprinco.com buffer spring - it’s like 15% less spring rate ($20).
The clamp-on SupArms AGB ensures the tightest fit and no loss of gas, and allows adjustment from zero to max gas.
The 0.125” gas port allows, well, max gas (the holes in gas blocks max out at 0.125”, hence “max”).
The yellow Sprinco buffer spring allows the platform to cycle with less gas.
In case it’s relevant, my buffer was a standard carbine buffer, and the barrel is an 11” Kak.
Then it’s just a matter of testing and tuning, and recording the results.
You test by setting the SuppArms AGB to 2/3 open. Max is 4.5 turns from closed, or 18 clicks. So start at 12 clicks from closed, only putting one round in the mag at a time and shooting, and observing the ejection trajectory of the spent cartridge and if the bolt locks open with the (now) empty mag.
Start with supersonic unsuppressed for the baseline, and then subsonic suppressed, then supersonic suppressed.
here are my settings, FWIW:
Supersonic unsuppressed: 9 clicks
Supersonic suppressed: 6 clicks
Subsonic suppressed: 12-13 clicks.
Other advice: don’t use grease on your BCG, it will gunk up and you may experience a failure to lock open on empty prematurely; use a high temp oil like Sprinco’s Machine Gunners Lube (they’ll send you a small one with the yellow spring) works wonders.
Hope this helps! This combo of parts give you all the flexibility you need to adjust as necessary to cycle your carbine.
