Cartridge Runout

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Pete
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Location: Penrith

Cartridge Runout

#1 Postby Pete » Thu Feb 08, 2018 4:26 pm

Question : When people are about their run-out figures are they expressing +/- of 0
Or are they generally talking the extreme spread for lack of a better term? ie 4" (+2 and -2 = 4)
Hope the above makes sense.
Cheers
Pete

DenisA
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Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

Re: Cartridge Runout

#2 Postby DenisA » Thu Feb 08, 2018 5:13 pm

I use Redding comp dies and a Forster Co-Axe. I measure the neck run out of approximately 5 random cases (maybe a few more to find an upper limit) of the batch every time I re-size brass. Only to keep an eye on things. I have records of every batch I prep in case I need to refer back to it if there's suddenly a problem with a load. I normally find I record neck run out as .001" +/- .001". Most are close to .000 but every now and so often one comes up that measures .0015". I don't believe it effects accuracy at that level, even if they're jumped.

Gyro
Posts: 349
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: Cartridge Runout

#3 Postby Gyro » Thu Feb 08, 2018 5:49 pm

Pete wrote:Question : When people are about their run-out figures are they expressing +/- of
Or are they generally talking the extreme spread for lack of a better term? ie 4" (+2 and -2 = 4)
Hope the above makes sense.
Cheers
Pete


I suspect it means the amount of bullet nose eccentricity/deviation from the cases true axis. So when it's said as "0.0015" run out, that means 3/4 of a thou per side ?

DenisA
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Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

Re: Cartridge Runout

#4 Postby DenisA » Thu Feb 08, 2018 8:33 pm

In that case I talk about the ES.

bruce moulds
Posts: 2326
Joined: Sun Jun 19, 2005 4:07 pm

Re: Cartridge Runout

#5 Postby bruce moulds » Fri Feb 09, 2018 5:17 pm

the term often used to describe this leaves no room for doubt.
it is total indicated runout or t.i.r.
for t.i.r. the axis of the bullet is 1/2 the reading from centre.
if your measurement is consistently 0.000 there is a good chance that there is a measuring technique problem.
just how much t.i.r. will affect long range accuracy is open to debate.
some believe that bullets jumped a lot will shoot better than jammed bullets with a lot of t.i.r.
then we should realize that probably no chamber has its axis absolutely concentric and paralell with the bore axis.
this is why we look for good gunsmiths, because they care enough to come close.
crooked chambers often shoot better with jumped bullets, even vld.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

Matt P
Posts: 1272
Joined: Mon Nov 14, 2005 8:22 pm

Re: Cartridge Runout

#6 Postby Matt P » Fri Feb 09, 2018 8:20 pm

bruce moulds wrote:the term often used to describe this leaves no room for doubt.
it is total indicated runout or t.i.r.
for t.i.r. the axis of the bullet is 1/2 the reading from centre.
if your measurement is consistently 0.000 there is a good chance that there is a measuring technique problem.
just how much t.i.r. will affect long range accuracy is open to debate.
some believe that bullets jumped a lot will shoot better than jammed bullets with a lot of t.i.r.
then we should realize that probably no chamber has its axis absolutely concentric and paralell with the bore axis.
this is why we look for good gunsmiths, because they care enough to come close.
crooked chambers often shoot better with jumped bullets, even vld.
keep safe
bruce.

Depends who cuts the chamber !!

bruce moulds
Posts: 2326
Joined: Sun Jun 19, 2005 4:07 pm

Re: Cartridge Runout

#7 Postby bruce moulds » Fri Feb 09, 2018 8:44 pm

matt,
you can't do better than humanly possible with the tools and machines available.
many don't reach this goal due to lack of try problems.
pretty soon the word gets around who does try.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

Gyro
Posts: 349
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: Cartridge Runout

#8 Postby Gyro » Sat Feb 10, 2018 5:57 am

I do believe Matt chambered both Rods guns for the Canada shoot the other day !!

I do my own and then I absolutely totally know it's right. It's not rocket science but you still need to get someone to do it properly to a high standard to what is considered the current best practice.

Of course you can never have too much accuracy but maybe ya don't need the most accurate gun on the range to get a podium finish, especially in bloody hard conditions ?

'Tis another large topic really and an interesting one and is absolutely related to one word I suggest : concentricity.

I blueprint my case sizing dies too so I absolutely totally know they are straight. It makes for a whole lot of shagging around but puts my mind at rest. The idea of checking for loaded round runout seems bizarre to me.

I'm still learning heaps which I guess is good as it keeps you coming back. Might try a tuner next !

BTW my total of barrel chambering jobs is only about a dozen !! Regards Rob Kerridge.

Wal86
Posts: 132
Joined: Sun Nov 20, 2016 5:10 pm
Location: Kilmore, VIC

Re: Cartridge Runout

#9 Postby Wal86 » Sat Feb 10, 2018 7:03 am

Gyro wrote:
'Tis another large topic really and an interesting one and is absolutely related to one word I suggest : concentricity.

Regards Rob Kerridge.



The word I would suggest : Total runout

Total runout indicates straightness, profile, and angularity.. It applies to an entire surface simultaneously instead of an individual concentric point

Gyro
Posts: 349
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Location: New Zealand

Re: Cartridge Runout

#10 Postby Gyro » Sat Feb 10, 2018 7:37 am

But Wal all items made " in the round " have a central axis ? A neutral axis ? It's that simple ?

The bore in a rifle has an axis and that particular axis likely has a big long gradual bend in it. Hence modern chambering practice dials in just that part of the bore at the chamber end to get the bullet the supposed best start down the bores axis.

And obviously if we want to aim the case-bullet assembly straight down the bores axis then 'runout ' or relative misalignment between the bullets axis and the cases is gonna slam the bullet ( especially a jumped one ) just slightly into the bore "on the piss " ?

Perhaps it's all just theory but it rings true for me.

So an honest attempt to control this stuff and off to the range we go.

Wal86
Posts: 132
Joined: Sun Nov 20, 2016 5:10 pm
Location: Kilmore, VIC

Re: Cartridge Runout

#11 Postby Wal86 » Sat Feb 10, 2018 3:43 pm

Gyro wrote:But Wal all items made " in the round " have a central axis ? A neutral axis ? It's that simple ?

The bore in a rifle has an axis and that particular axis likely has a big long gradual bend in it.



This is called the neutral axis of the bore.. This axis is subject to bending..

Concentric dialing only indicates "central axis" at point of indicating (runout) and doesn't detect angular compensation.
Pending methods/techniques used of course..

I believe if you not dialing both angular and radial detection your only doing half a job...
But this is only my opinion..
Last edited by Wal86 on Sat Feb 10, 2018 6:02 pm, edited 7 times in total.

Gyro
Posts: 349
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: Cartridge Runout

#12 Postby Gyro » Sat Feb 10, 2018 4:16 pm

Wal you're gonna drive me to drink ! Where's the fridge ....


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