Thanks for the length measurement.
(Not sure how good these pictures are. I took one of two 4831 brass and two retumbo. The shiny ones are the 4831 ( tumbled brass). The dull ones retumbo.)
In the first picture the two on the left is from the Retumbo loads and the ones on the right are the 4831. So on the Retumbo loads there is scratching or marking between the 6.5 and the 284 that look like it is made from the bolt. I also had this same marks on my brass and then another little mark which I'm pretty sure is the little pin in the bolt face marking on the brass. This was all done at 52.5grn of 4831sc. Also the bolt was tight when lifting a fired round. So I figured at this point I was over pressure and did not want to go any higher. I backed off a grain and made some loads. They seem to be ok with bolt lift and only a very faint mark on the brass without the round pin mark. But the volicity was under 2800fps on the chrono I have.
I just thought of something...I was also using another chrono graph at the time that gave me lots of trouble so my volicity may have been higher than I thought. With the old it always would the 51.5grns I was about 2770fps at muzzle. I now have a different one. But as anyone know the loads need to be shot at some distances to be valid. Good thing is the chrono I use now actually seem to measure the volicity pretty good. So I will be interested to see what Brents input is on your cases.