I built a 6 dasher Howa mini with factory 6ARC barrel reamed out, and cut/threaded at 16”.
First 30 rounds of virgin Peterson brass went great!
I have to do a little clean up on the bolt face to prevent it from scratching case head on extraction.
Found a few promising loads.
On to reloading issue…
Reamer print shows .460” shoulder diameter.
This is reflected in a once fired brass shoulder diameter of .460”
I have an rcbs matchmaster full length bushing die. I measured a virgin case with 6mm bullet and got .266” loaded neck diameter, so I purchased a Redding .264” bushing.
When I tried to size a case, I realized I needed to remove material from shell holder to get any movement - as it was no bumping back was occurring. I took enough material off to allow for this. I then set .375” datum measurement back .002”. I chambered the resized brass and it was extremely difficult to chamber and harder to extract.
I noticed a shiny ring just below the shoulder where the brass was clearly contacting chamber and grabbing.
I measured the diameter of the sized case at shoulder and got .463” (average across 5 that I then confirmed with, all .462-.464”).
I called RCBS and the woman pulled a print and said the shoulder dimension of that die should be .456” - this makes sense to me.
She told me to box it up with fired and sized case and they’d trouble shoot and send it or a replacement back.
I even tried bumping shoulder less, at .0005, and .001, and still got the increased shoulder diameter.
Before I ship this off, does anyone have any idea if I might be doing something to cause this? Or any way to confirm that internal shoulder diameter measurement of the die?
I’m assuming it’s got to be a bad die. But I’m not a seasoned reloader and may be missing something obvious.
Any ideas?
Recap:
All brass virgin, fired once, and sized below case spec length.
Virgin brass .452” shoulder diameter, 1.238” base to .375 datum.
Fired brass .460” shoulder diameter, 1.2445” base to .375” datum.
Sized brass .463” shoulder diameter, 1.2425” base to .375” datum.
Picture of the ring:

First 30 rounds of virgin Peterson brass went great!
I have to do a little clean up on the bolt face to prevent it from scratching case head on extraction.
Found a few promising loads.
On to reloading issue…
Reamer print shows .460” shoulder diameter.
This is reflected in a once fired brass shoulder diameter of .460”
I have an rcbs matchmaster full length bushing die. I measured a virgin case with 6mm bullet and got .266” loaded neck diameter, so I purchased a Redding .264” bushing.
When I tried to size a case, I realized I needed to remove material from shell holder to get any movement - as it was no bumping back was occurring. I took enough material off to allow for this. I then set .375” datum measurement back .002”. I chambered the resized brass and it was extremely difficult to chamber and harder to extract.
I noticed a shiny ring just below the shoulder where the brass was clearly contacting chamber and grabbing.
I measured the diameter of the sized case at shoulder and got .463” (average across 5 that I then confirmed with, all .462-.464”).
I called RCBS and the woman pulled a print and said the shoulder dimension of that die should be .456” - this makes sense to me.
She told me to box it up with fired and sized case and they’d trouble shoot and send it or a replacement back.
I even tried bumping shoulder less, at .0005, and .001, and still got the increased shoulder diameter.
Before I ship this off, does anyone have any idea if I might be doing something to cause this? Or any way to confirm that internal shoulder diameter measurement of the die?
I’m assuming it’s got to be a bad die. But I’m not a seasoned reloader and may be missing something obvious.
Any ideas?
Recap:
All brass virgin, fired once, and sized below case spec length.
Virgin brass .452” shoulder diameter, 1.238” base to .375 datum.
Fired brass .460” shoulder diameter, 1.2445” base to .375” datum.
Sized brass .463” shoulder diameter, 1.2425” base to .375” datum.
Picture of the ring:
