Wish I had some gauges. I’ve owned a few enfields and still own a no4 mk1 303. It’s my favorite. I shoot it quite a bit. I can slug the barrel for you but not the throat. The throats are wide open on all that I’ve seen anyway. I’ve never checked the headspace. I shoot new brass then check to see how much it stretched. If the stretch is acceptable to me then I only necksize.