Shifter barrel adjuster question, is the metal body supposed to sit flush?
 

Flush with the plastic outer body? Not able to screw it in any further.


https://cimg8.ibsrv.net/gimg/bikefor...30ee2418e4.jpg

I think that you have the plastic outer body reversed

When setting the adjuster initially before snugging the cable down in the holdfast, I try to consider which way I'll normally have to adjust the particular cable I'm dealing with.

Usually my adjustments are going to be to "shorten" the cable, so mostly they are screwed most of the way in and I'll only have a few turns of thread to "lengthen" it.

For times I was unsure because I was new to that part, then I put it in the middle of it's range.

Thank you for pointing out that the adjuster effectively shortens and lengthens the housing, it doesn't adjust the "tension" as it is so often described. The return springs set the tension.

If you mean the ribbed metal part is standing proud of the plastic knob, Normally that is how it should be, and you pull the knob up against spring tension to engage the ribs of the knob with the ribs of the metal barrel to turn it.