Id bank on .342" I wouldn't feel at all uncomfortable in turing them to clean up if youre using a bushing die, or the lee collet die. If I was going to use an expander on these cass id turn them to clean up 50%. Expansion will be about the most id want to see, but you shouldn't have any trouble with necks splitting too fast. Im loading for a7mmREM mag that has .009" total expansion on firing, and the cases are lasting well. ive got 3 cases that are at their 7th loading, and the other 150 are at the 4th loading with no signs of problems... comprable dimensions to your setup if you turned them to full cleanup, more or less. For those that think .002" per side is too tight to come from a factory chamber... it ain't. A number of savage barrels ive worked with, and at least 2 remingtons recently have had .005" total clerance or less. One savage with federal brass .016" neck thickness, had .003" total. Case life is super /ubbthreads/images/graemlins/smile.gif
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How much to turn necks?
- Thread starter Alan Griffith
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<font color="purple">DW Writes: i do agree that measuring fired brass is not an exact thing for chamber diameter, but it will get you in the ballpark,probably within .001.
DC responds: Using 5 different brands of cases will yield 5 different case neck thickness dimensions. Also the cases will be of different temper or hardness, so they will never be even close as to figuring the chamber neck dimension from a fired case.
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.001 is the often quoted spring-back (I have no evidence it's accurate), but to say "never be even close" is meaningless without quantifying. Never be within .003? Even with one brand of brass from different batches, hardness varies. FC is known to be softer than other brass. Even so, the diff between the hardest and softest brass will not be more than .001 (spring-back of .001 to .002 - just my wild *** guess).
GSSP --> It's really easy to make a chamber cast with Cerrosafe (it melts below the boiling point of water).
I would guess .002 clearance is too tight for a hunting rifle.
<font color="purple">DW Writes: i do agree that measuring fired brass is not an exact thing for chamber diameter, but it will get you in the ballpark,probably within .001.
DC responds: Using 5 different brands of cases will yield 5 different case neck thickness dimensions. Also the cases will be of different temper or hardness, so they will never be even close as to figuring the chamber neck dimension from a fired case.
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[/ QUOTE ]
.001 is the often quoted spring-back (I have no evidence it's accurate), but to say "never be even close" is meaningless without quantifying. Never be within .003? Even with one brand of brass from different batches, hardness varies. FC is known to be softer than other brass. Even so, the diff between the hardest and softest brass will not be more than .001 (spring-back of .001 to .002 - just my wild *** guess).
GSSP --> It's really easy to make a chamber cast with Cerrosafe (it melts below the boiling point of water).
I would guess .002 clearance is too tight for a hunting rifle.
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From the master himself Case necks by BB
Alan Griffith
Well-Known Member
Conclusion on my rifle's neck chamber dimensions: .342"
I did a nifty little trick of taking a .350" speer lead ball, jaming it lightly into the mouth of a case and mostly chambering it into the chamber. The neck swaged the .350" ball to .342". Needed a small diameter plastic rod to drive the ball out of the chanbers neck.
My math tells me:
.342" neck diameter minus .001" spring back = .341"
.341" minus .003" clearance = .338"
.338" minus .308" bullet diameter = .030"
.030" divided by 2 = .015" thickness for each wall.
I seem to recall reading stuff over the years that .015" used as a common goal.
For now, I'm thinking of just taking the top 27 cases which read the most variance and shaving them down to a max thickness of .0165". This should allow all 100 cases to have a max variance of .0015" or less.
I did a nifty little trick of taking a .350" speer lead ball, jaming it lightly into the mouth of a case and mostly chambering it into the chamber. The neck swaged the .350" ball to .342". Needed a small diameter plastic rod to drive the ball out of the chanbers neck.
My math tells me:
.342" neck diameter minus .001" spring back = .341"
.341" minus .003" clearance = .338"
.338" minus .308" bullet diameter = .030"
.030" divided by 2 = .015" thickness for each wall.
I seem to recall reading stuff over the years that .015" used as a common goal.
For now, I'm thinking of just taking the top 27 cases which read the most variance and shaving them down to a max thickness of .0165". This should allow all 100 cases to have a max variance of .0015" or less.
davewilson
Well-Known Member
GSSP, i'll bet if you turn them all down to .014 you wouldn't have to use the expander in your FL die and would end up with more accurate ammo.this might be an interesting experiment for you.try different neck thicknesses and loading proceedures to find out if one nets you better groups than the other.this is exactly what we all love to talk about on here!
Alan Griffith
Well-Known Member
Dave,
Hummmm! Interesting! Let's see:
.342" - .001" = .341"
.341" -.003" = .338"
.338" -.308" = .030"
.030" / 2 = .015"
Trim that .015" to .014".
I'll try a case or two from the worst bunch of 11 and let you know what happens.
Hummmm! Interesting! Let's see:
.342" - .001" = .341"
.341" -.003" = .338"
.338" -.308" = .030"
.030" / 2 = .015"
Trim that .015" to .014".
I'll try a case or two from the worst bunch of 11 and let you know what happens.
davewilson
Well-Known Member
.014 is .006 clearance on a loaded round where .015 is .004. run a case in your full length die without the expander to open the neck back up and tell us what the outside measures.if it doesn't squeeze the bullet too much, this is the way to go to get straight ammo.i have a FL die on order from forster right now to do just that.my die will be around .003 less than a loaded round.this is what "master B" recommends!
