A bullet will go in just over half way past the crown. It feels like the case goes into the chamber up to the top of the rim gap, leaving room for the extractor. But I can't really tell.
Muzzle doesn't matter much if the bullet is driving into the lands in the throat/lead
You need to get a caliper and start measuring... the neck might be to tight.?
Your field gauge only tells you the headspace is not out of spec.
You need a go gauge to see if minimum HS is good.
Also being a replacement barrel we have no idea if the chamber was ever finished correctly... any close possibilities of another cartridge these where know to be chambered in?