Why no Crown Continuum in .177??

Agreed, the air efficiency of a .177 in 380mm is very high, in fact it's probably closer to the ideal length than people think.

I am using my standard 600mm Crown STX barrel in a Continuum, IMO again the 700mm on a Crown is just too long anyways and after trying the Impact .30 700mm in the Continuum there is no real gain over the 600mm.

You could just put a standard .177 Crown barrel on a Continuum, but you lose the advantage of being able to fit it in the Impact length case, having said that it is easy for anyone with a lathe to shorten the barrel assembly.

The Superlite barrel nut assembly is the same two rear pieces as are used on the assembly with the steel outer, so you could remove these parts from the nut on another caliber and swap them to .177 (I am considering doing this in .30).

Travis from AGD had the right idea though IMO, the Continuum in the case with .22 380mm barrel fitted and a 600mm .30 barrel & probe and that pretty much covers every shooting angle, which is exactly what I have done.