Dennis, Speer supplies a FoF AR BCG that I’ll have in a couple weeks; will post pics. From what I’ve seen it looks similar to the SimFX and Winchester SRTA bolt.
The dedicated factory Glock G17T trainer pistols work fine with most SimFX or Speer fodder; some of the SimFX-made conversion kits work best with SimFX cartridges.
The G17Ts don’t run well at all with certain SimFX blanks, only made for the SimFX kits.
The Speer 5.56 FoF is advertised as having a much shorter safe-distance (1ft); some of the SimFX 5.56 has a minimum 10ft or more SD, and that’s only with specific SimFX brand PPE.
As soon as I test the 5.56 FoF stuff I’ll report back with more info.