450Bushmaster.net

I was priming my 284 case after firing and came across (1) that would not fit into my Lee "Auto prime" tool. Everything looked just fine on the outside.
Sooo! I Checked the extractor groove, It was .416! All the others were .404 - .406. Some as wide as .410! The 284s new are .404 - .406!
I had just cleaned, sized & deprimed them. So, I have no idea of which charge they recieved. Anywere between 39.5 to 42 of Lil gun with a 230grn. FMJ. My thoughts are, With a tight chamber and a good strong lock up! Where is the brass to go? The only place not supported. the extractor grove............. Any thoughts!!!!..........Anyone!!!!

It may not just be the .450 B that has this issue. My .284 based cases were cut down from used .284s and .284/6mm cases and a few of them had this issue when I tried loading them the first time. It may be a rebated rim thing. I wonder if the .50 b cases act the same?
BD

I posted about an extractor groove problem. Could this be a sign of over pressure? When, the extractor groove expands from .404 to .416? And, everything else remains the same? Or, Is this just a wear problem of a rebated rim like BD1 pointed out? I'm thinking along the lines of a copper pressure disk test for pressures. Thinking out of the box here. I have some recoil and mag things to post. But, want to get this out of the way 1st. Please let me know what you are thinking!............Anyone!
Happy Shooting!

I'm thinking that this maybe the way a rebated rim case deforms from pressure over time? On a "standard" bottle necked case you get measurable case head expansion at the very base of the case head, on a belted case you get measurable expansion of the case head just forward of the belt. Maybe on the rebated rim cases the area of the head at the extractor groove gets incrementally compressed over time causing it to flatten out and gain diameter? It kind of makes sense as in the rebated case this area is proportionally smaller relative to the case "head" diameter.

BD