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My 30BR barrel arrived today! I have 2 cases - 150 Lapua "6mmBR norma" headstamp that I plan on using, and 20 R-P "7mmBR Rem" headstamp cases that I purchased to practice my brass forming skills on.
Th 6mmBR Lapua cases fit the chamber tightly, while the Rem 7mmBR cases are a little loose - they probably have 0.002" wiggle room at the base.
I've purchased a Redding type-s FL Bushing die, which I was planning on having machined to accept the 30BR neck (0.333" in my case) like has been recommended on this board and others. I find that the 7mmBR brass fits into the die with just a little less slop than it fits into the barrel, while the 6mmBR brass won't go in all the way - it gets tight about 1/8" from bottoming out- -in other words, it don't go into the die all the way to the shoulder.
My assumption is that my chamber is cut for "norma" and not Rem BR brass, which appears to be a little smaller in diameter.
Should I modify the neck and use this 7mmBR FL die, or should I try to send it back, and get a 6mmBR die to modify (open up the neck) instead?
I could probably also hone this 7mmBR die until the brass fit also.
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A Type 'S' FL bushing die is designed to resize the cases down. If your Lapua brass won't go in the last 1/8", that just means the shoulder of the brass out of the box is maybe .001-.002" bigger than the die (I doubt it's sticking at the web).
But that's not a bad thing from my perspective. Lube a Lapua case and run it up into the die, then measure the shoulder and the web and compare that to the brass out of the box.
If it's just bringing in the shoulder and base .001" or so that's fine.
After fire-forming your brass in your chamber, measure the shoulder again. If the difference between fire-formed brass and the brass coming out of your Type "S" FL sizer is more than .003" or so, then you might want to consider having the die honed and opened up a little. But until then, leave it the way it is. It sounds like it's actually a pretty good fit.
Read this article by Jim Carstensen: http://www.6mmbr.com/CarstensenJLC01.html
Bottom line: You actually want that die to bring in the shoulder and the base of your fired rounds a little bit. Only if it's working the shoulder TOO MUCH do you want to hone it.