what doesn't work?
Geissele SSP trigger doesn't reset with most 9mm AR Colt-compatible bolts. SSP trigger does reset with Foxtrot Mike FM-9 Colt-only 9mm AR bolt.
Colt-pattern Hahn dedicated magwell adapter
Caliber: 9mm
Metalform 32rd mags
Barrel length: 16" (Macon Armory enhanced feed cone)
Bolt weight: std (15.5oz)
Buffer weight: 6oz
Additional details: my Geissele SSP trigger did not reset with KVP, AIM, Faxon, Spinta bolt carriers. However if you release the trigger, and pull the bolt back again with the charging handle (unfired round extracted from chamber, new round loaded), with the finger off the trigger, it cocks the hammer. In comparing the pickup lug on the bottom of these bolts with the pickup lug of a mil-spec 5.56 BCG, they are about .040" shallower than the 5.56 carrier, consequently, they don't press the hammer down as far, and it doesn't engage with the disconnector.
I'm shooting strictly unsuppressed.
tried it with KVP, AIM, Faxon, and Spinta bolts. all the same. also tried a 2nd SSP trigger lower, same result, doesn't reset. The bottom of the bolts I have is too shallow to push down enough to reset the SSP trigger, when compared to a regular AR15 BCG. Guess the SSP needs that little extra nudge to reset that would normally be present with the AR15 BCG.
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What does work:
I purchased a Foxtrot Mike FM-9 Colt-only bolt and that has a different shape on the bottom of the pickup lug, the extra material there pushes the SSP hammer down far enough to reset, and still is within the "envelope" of the mil-spec BCG dimension. So everything is good now.