CSLA M16 variants are not compatible with most vanilla or GM STANAG 5.56 magazines, when they obviously should be. Compatibility is obviously possible since the vanilla 30rd Reload Tracer Yellow magazine is compatible, it just needs to be expanded. I'm pretty sure the recently-introduced magwells/magazine proxies tech should allow all 5.56 STANAG mags to be compatible without needing a prescriptive list of classes.