Need some help with Neck turning dimensions and bushing choice

mux 69

mux 69

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How's it going , not new to reloading, but fairly new to the precision game , I've got a 6 BR Norma on order with a .268 reamed neck chamber, brass should be in any day now , need a little advice on what diameter I should turn the brass too and once I turn my necks to a certain size how do I determine bushing size , thanks in advance for any advice,
 
you want 2 thou neck clearance on the chamber, so a loaded round should measure 0.266, normally when the chamber is spec'd 0.268, that is the size your loaded round needs to be. Your bushing needs to be 1-2 thou smaller then a loaded round, so if a case with a bullet seated measures 0.268 you will want a 0.266 and 0.267 bushing, and perhaps even smaller
 
you can order the bushings, if you are using Lapua brass there is a good chance you won't have to neck turn, the last few boxes I have received have had a neck diameter of 0.2675 with a bullet seated, at the very most all you may want to do is skim turn them, I don't bother with that, just load them and shoot them
 
seat a bullet and measure the neck with a bullet seated, there is small lot to lot variances in brass
 
Not to confuse you but;
Chamber neck dia........... .268
Neck dia with bullet seated .266
Bushind dia..................... .264
That gives you the .002 expansion needed when seating a bullet.
 
b72471 said:
Not to confuse you but;
Chamber neck dia........... .268
Neck dia with bullet seated .266
Bushind dia..................... .264
That gives you the .002 expansion needed when seating a bullet.
Click to expand...

I agree, just depends on what number he got with the barrel, when my chambers are spec'd at .330 and .269 that is the size my loaded ammo has to be, where as something like a savage 6br has a .272 neck which is the reamer dimension and loaded ammo needs to be .270. At the end of the day he needs to confirm what the number is from whomever is supplying the barrel
 
Not sure what you mean by specd at .330, it's a Manson reamer .268 neck dimension 105 freebore on a Bartlein barrel, the real reason I'm asking is because I want to order my dies and bushings from Brownells, and just want to make sure I get the right sized bushings
 
So if your reamer is spec'd at 0.268 then your brass should be turned to 0.265. You will need a 0.264, 0.263 and 0.262 bushing. With the 6br and 6ppc I run 1 though neck tension for easy bullet seating, it's also given me the best accuracy
 
If your reamer is spec at .268 then you rifle chamber will have a neck diameter of .268. As mentioned you should have at least .002 case neck to chamber clearance, if not .003 to be safe. Measure a 6 BR case with bullet seated and if it would be .268 for example then you do not have sufficient clearance. I believe you would have to turn .0015 off your case neck to achieve .003 clearance. My 6BR Norma ammo measures .269 with a loaded round.(unturned) My Manson reamer was speced at .272 neck size. This gives me the .003 clearance I desire. Works for me.
 
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