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Concentricity

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Wing master View Drop Down
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AKA StraightShooter

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wing master Quote  Post ReplyReply Direct Link To This Post Topic: Concentricity
    Posted: 31 May 2017 at 15:33
I just finished reading an article about concentricity
of reloaded ammo. Basically how straight the bullet is
seated into the case.

The article made it sound like it had quite an effect on
accuracy,

Sinclair makes a (probably expensive) dial indicator
tool to check this.

Do any of you do this with your reloads? What are your
thoughts on this increasing accuracy?

Wing master
I have always considered myself to be quite the bullshitter, But ocasionally it is nice to sit back and listen to a true professional......So, Carry on.
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Irish Bird Dog View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Irish Bird Dog Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 15:49
Hornady makes a tool like that too...basically a dial
indicator reads surface of the bullet in case as you
rotate the loaded round in the tool. Others might make
such a unit too. Many seem to believe in the truer the
bullet is to zero run-out the more accurate it will be.
Just one of many factors to the "perfect" loaded round.
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lizard View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lizard Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 16:32

I use the Hornady concentricity tool on my hunting rounds.  Does it really help the accuracy?  I would like to think so.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote deaddog Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 16:36
Some cartridges especially with long necks benifit from case neck
turning. If all of your bullets are seated to the same depth aren't they
going to get straightened out by being squeezed and spun down a 24"
inch or whatever length tube? I like reloading accurate rounds. I have
tried most benchrest tricks and know what works for me and what the
return on my time investment compared the the gain if any each step or
trick will provide. I don't weigh and sort my primers by like weights. But I
may sort my bullets by weighing each one and only use exact same
weights on a hunting trip. I only use the same brands of brass- I don't
mix military with commercial either, but I don't weigh them but I trim to
the same length. Many things can be done. What ever gives you piece
of mind or better accuracy do it. This is just a long winded way of
saying turning your necks is a much better use of time than running
them on a dial caliper. The little that I've used them showed me how
sensitive the guage was and how little I could do to fix it other than turn
the necks. Epiphany- buy new brass or turn necks. Don't waste time
measuring runout.

DD
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BEAR View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BEAR Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 23:43
concentricity an interesting concept.

But the real question is concentric with what????

Concentric with the outside of the neck?
Concentric with the inside of the neck?
Concentric with the outside of the case body?
Concentric with the case base?

None of these matter. what matters is concentric of
the bullet with the axis of the bore. But chambers
and bores are cut separately, on different machines,
by different people at different facilities. So they
can never be concentric (except for luck).

Then remember that bullet jackets are not uniform
(cold formed). So if the bullet isn't perfectly
uniformed, the axis of gyration isn't concentric.

How much does the brass case deform when chambered and
thee locking lugs rotated? Since most folks use
rimless shells and neck form only, one would think a
decent amount of movement occurs at the shoulder.
Wouldn't it be easier to align the bullet and bore
with a rimmed case? Maybe that is why the 219 wasp
and improve zipper were so accurate in the 1950s when
powder/primer/brass/bullets were not as consistent as
today.

Just rambling thoughts,,while waiting for it to warm
up so I can wash the boat.   42 oF while I'm in NY
drinking coffee in a keystone gas station!



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RobertMT View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RobertMT Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2017 at 05:28
I was shown a easy way to check ammo. Take a mirror tile and slowly roll round on it, if you can see any wobble in bullet tip, you can figure you have more than .003" concentricity issue. You can then take carbon paper, taping it over paper on another mirror tile and rolling round on first mirror, while keeping bullet tip against carbon paper, you'll trace line, if it appears to have waves, you know you have wobble.

How you check chamber for alignment, is to roll case fired in your rifle, on mirror, watching base and mouth for wobble. If your chamber isn't true, best solution is to mark and index round in chamber. If your fired brass is true and wobbles after reloading, you need to find where you're causing it, I check after sizing and again after seating bullet.

If you check factory rounds, many will have visible wobble and still shoot fine.

If you decide to get concentricity gage, for the small difference in cost, spend the extra $20 for Sinclair tool.

I would suggest upgrading to FL bushing die and match type seating die, they will give better accuracy return, for your investment. The expander on standard dies, is the cause of most concentricity issues, along with overworking your brass.
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Wing master View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wing master Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2017 at 16:47
Thanks for the input guys.

After thinking about it I wonder if the concentricity of
the bullet in relation to the case is why I usually get
better accuracy by seating the bullets ogive as close to
the lands as possible without actually touching.

A few years ago when I got my .308 I decided to spend a
little more money and buy Lapua brass. I think the
quality is good enough that neck turning isn't
nesassary. I liked it well enough that I bought Lapua
brass for my 6.5 project.

Wing master
I have always considered myself to be quite the bullshitter, But ocasionally it is nice to sit back and listen to a true professional......So, Carry on.
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