NECK CLERANCE - IS IT IMPORTANT?

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John T
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NECK CLERANCE - IS IT IMPORTANT?

#1 Postby John T » Wed Mar 13, 2019 4:28 pm

Hello All.

Old wisdom says that neck clearance (NC) should be from 0.003 to 0.004. Why, I don't know.

Only with very well turned necks could you claim to have consistent NC of 0.004, 0.003, 0.002 or 0.001. Which NC delivers the best consistency, and why?

What do the buffalo boys (avowed non-turners) have to say? They don't care if their case necks have humps and hollows of 0.002 or more, so long as they chamber#.

If NC is not important, neck turning is irrelevant, save for what some call a "tidy-up"#.

In short, maybe we should not be concerned about neck OD, save that the necks do not interfere with chambering and extraction, and concentrate on consistent neck ID, using an expander that keeps the necks in-line.

I anticipate some ripping debate on this one.

Debate on the amount of neck tension will follow.

Regards,
John T.
13.3.19

Gyro
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Re: NECK CLERANCE - IS IT IMPORTANT?

#2 Postby Gyro » Wed Mar 13, 2019 5:53 pm

Some more waffle from me : for me it's a similar question to asking if a "through the headstock" chamber job is actually better than a "between centres" one.

I take it that part of Johns question alludes to the importance of supposedly starting the bullet as perfectly on centre with the bores centreline as possible. Concentric.

Some brass is not good re having relatively even walled case necks. Even supposedly good brass ! So if the case has more wall thickness on one side than the other then straightaway the bullet is sitting a little off the bores centreline, and therefore not where it's supposedly ought to be to get that perfect start on its journey.

I suspect, except in extreme cases it doesn't matter and would be very hard to prove either way, considering how many other dynamics are taking place when a shot is fired ?

bruce moulds
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Re: NECK CLERANCE - IS IT IMPORTANT?

#3 Postby bruce moulds » Wed Mar 13, 2019 7:43 pm

2 questions.
who are the buffalo boys?
what is through the headstock and between centres chambering?
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

Gyro
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Re: NECK CLERANCE - IS IT IMPORTANT?

#4 Postby Gyro » Thu Mar 14, 2019 3:26 am

bruce moulds wrote:2 questions.
who are the buffalo boys?
what is through the headstock and between centres chambering?
bruce.


I shall refrain from answering your question Bruce about the chambering method as it will take us a long ways away from Johns' topic question here. Maybe start another question on that one ?

I just looked at the pure bullet 'alignment' part of Johns' question re case necks. That's one part, but maybe the clearances we use impact on what happens in other ways ?

I'm now sure that clearance for the bullet in the freebore/throat section of the chamber matters, but shooters have run VERY small clearances around case necks for ever and shot well. But maybe that's only ok so long as you have a very accurate system of case prep to make sure everything stays in line ?

Maybe the modern trend of "no neck turn" chambers just simply keeps people out of trouble in this area, especially since actually preparing truly accurately consistent necks aint as easy as many might think. The usual tools I see being used are at best an honest attempt.

ben_g
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Re: NECK CLERANCE - IS IT IMPORTANT?

#5 Postby ben_g » Thu Mar 14, 2019 12:32 pm

Through my own mistake I overturned the necks on 300pieces of 284brass, my chambers are no turn necks which I think are 0.317 (offhand). My loaded rounds only measure 0.311 and the barrels shoot wonderfully!

I have got through one barrel and 600rounds into a second barrel and am only just starting to see some split necks now.
I don’t think the extra clearance has hurt my accuracy, both barrels have proven to be capable of a high standard of accuracy.

pjifl
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Re: NECK CLERANCE - IS IT IMPORTANT?

#6 Postby pjifl » Thu Mar 14, 2019 3:38 pm

I have never met a newcomer who fully appreciates just how easy it is to degrade good cases with inadequate attention to detail during neck turning.

Most agree that, if neck turning standards are perfect, brass fired in a perfect chamber/barrel will have few or no problems. Even with very fine clearances.

BUT THEY ARE FORGETTING SOMETHING. ALL ENGINEERING HAS MANUFACTURING TOLERANCES. NOTHING IS PERFECT.

1/ EVEN THE BEST LOADED ROUNDS HAVE SOME RUNOUT.

2/ EVEN USING REAMERS WITH AN EXCELLENT SETUP, THEY CAN VERY EASILY CUT A CHAMBER VERY SLIGHTLY MISALIGNED WITH THE BORE. This is beyond your control. It is why good bores are honed rather than just reamed. Steels can have softer and harder patches which cut and ream differently. Honing or Lapping can produce more accurate and better finish than reaming. Diesel injector parts and pumps have exquisite fits. They are not left finish reamed.

All it takes is for some slight inaccuracy in one of these areas to result in some sideways jamming of projectile and neck to cause irregular velocities. This is much worse with the long bullets we use so copying short range BR practices does not make a lot of sense. Maintaining correct tolerances is terribly important in Engineering.

To some extent, the 3 to 4 thou total neck clearance I and others talk about is the result of years of experience. When I first heard of it from experienced early F shooters I was skeptical. Now I am not.

Like Ben, I once accidentally used some cases turned for a 0.310 neck in a standard 0.319 --- 284W neck reamer chamber. I had oodles left over from an earlier project. All now 'ruined' because I had lost access to the smaller neck reamer and did not want to go that way any more anyway with a new reamer. BTW, an inexperienced or careless person can blow up a rifle using standard cases in a severely under necked chamber. I wonder who then becomes legally responsible even with the barrel clearly labelled.

They shot very well. 400 x 284W cases represents a lot of money all down the drain. They did not split on one firing but I never subjected any to more reloading.

Unless cases I get are very very substandard, I will NEVER neck turn again. And then, only the slightest skim. There are far more things worth spending time on !

Peter Smith.

RDavies
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Re: NECK CLERANCE - IS IT IMPORTANT?

#7 Postby RDavies » Thu Mar 14, 2019 3:42 pm

ben_g wrote:Through my own mistake I overturned the necks on 300pieces of 284brass, my chambers are no turn necks which I think are 0.317 (offhand). My loaded rounds only measure 0.311 and the barrels shoot wonderfully!

I have got through one barrel and 600rounds into a second barrel and am only just starting to see some split necks now.
I don’t think the extra clearance has hurt my accuracy, both barrels have proven to be capable of a high standard of accuracy.

I also have a few batches of brass which were turned down way too far, or were turned down to suit a previous much tighter chamber and these also shot extremely well. I believe it was something like .010" clearance or a little more. I have had issues though when there was insufficient neck clearance, which caused higher ES/SD for some reason. I have no idea why .012" clearance works better than 1-2 thou clearance, but it just seems to be so.

bruce moulds
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Re: NECK CLERANCE - IS IT IMPORTANT?

#8 Postby bruce moulds » Thu Mar 14, 2019 5:56 pm

well 6mmbr said that 7mm has to have 0.004 clearance, so that has to be the best, period.
clearance and neck tension are 2 different things.
some br guys used to run zero tension, but they clean every group.
this could be very dangerous in our situation.
good annealing practice will help retain even wall thickness all the way around, as well as consistent tension through the life of the case.
as you minimize clearance, any variation in clearance becomes a bigger % of the clearance, and obviously the opposite applies as you increase clearance.
tension is about more than how much the sized neck expands with bullet seating.
it should be thought more of in terms of neck grip on the bullet.
this can be affected by spring in the neck, length of bullet in the neck, lubricant or not in the neck, expansion of the neck during seating, and probably other things.
while thickness of the neck is one of them, differences are not much, however consistent thickness is good here.
safety is the most important reason for adequate clearance.
still wondering who the buffalo boys are?
might help answer the question.
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

KHGS
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Re: NECK CLERANCE - IS IT IMPORTANT?

#9 Postby KHGS » Thu Mar 14, 2019 6:39 pm

pjifl wrote:I have never met a newcomer who fully appreciates just how easy it is to degrade good cases with inadequate attention to detail during neck turning.

Most agree that, if neck turning standards are perfect, brass fired in a perfect chamber/barrel will have few or no problems. Even with very fine clearances.

BUT THEY ARE FORGETTING SOMETHING. ALL ENGINEERING HAS MANUFACTURING TOLERANCES. NOTHING IS PERFECT.

1/ EVEN THE BEST LOADED ROUNDS HAVE SOME RUNOUT.

2/ EVEN USING REAMERS WITH AN EXCELLENT SETUP, THEY CAN VERY EASILY CUT A CHAMBER VERY SLIGHTLY MISALIGNED WITH THE BORE. This is beyond your control. It is why good bores are honed rather than just reamed. Steels can have softer and harder patches which cut and ream differently. Honing or Lapping can produce more accurate and better finish than reaming. Diesel injector parts and pumps have exquisite fits. They are not left finish reamed.

All it takes is for some slight inaccuracy in one of these areas to result in some sideways jamming of projectile and neck to cause irregular velocities. This is much worse with the long bullets we use so copying short range BR practices does not make a lot of sense. Maintaining correct tolerances is terribly important in Engineering.

To some extent, the 3 to 4 thou total neck clearance I and others talk about is the result of years of experience. When I first heard of it from experienced early F shooters I was skeptical. Now I am not.

Like Ben, I once accidentally used some cases turned for a 0.310 neck in a standard 0.319 --- 284W neck reamer chamber. I had oodles left over from an earlier project. All now 'ruined' because I had lost access to the smaller neck reamer and did not want to go that way any more anyway with a new reamer. BTW, an inexperienced or careless person can blow up a rifle using standard cases in a severely under necked chamber. I wonder who then becomes legally responsible even with the barrel clearly labelled.

They shot very well. 400 x 284W cases represents a lot of money all down the drain. They did not split on one firing but I never subjected any to more reloading.

Unless cases I get are very very substandard, I will NEVER neck turn again. And then, only the slightest skim. There are far more things worth spending time on !

Peter Smith.


Peter, you are so correct!!!!!!!!! The only important thing for me about neck clearance is that there is enough!!! A much more important consideration in my humble opinion is case length, I like to have a maximum clearance in this area of no more than .015". This does however require specialised measuring gauges, so don't get all carried away with this, unless you have access to the means to accurately carry out this measurement and the ability to actually carry out this measurement correctly. If you get it wrong the result won't be pretty! With over 40 years of professional gunsmithing under my belt it no longer surprises me just how often the "layman" gets important measurements wrong!!!
Keith H.

wsftr
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Re: NECK CLERANCE - IS IT IMPORTANT?

#10 Postby wsftr » Thu Mar 14, 2019 7:10 pm

Perhaps it went like this.....

In the beginning there was brass and it shot well
one day a shooter said let there be better precision and so turned necks.
there was better precision, then there were split necks
so the shooter said give me less clearance between the turned necks and the chamber and there was still better precision so the shooter said turned necks shoot better and my un-annealed brass no longer splits.

Then there was a buffalo boy and he said - give me modern brass with good tolerances and a larger clearance to fit my unturned necks. Buffalo boy annealed this brass and shot it. Buffalo boy won matches and trophies. Buffalo boy said the new brass is good and the necks don't split, buffalo boy drank beer instead of turning necks.

Ever since there have been religious discussions to turn or not turn brass necks!

IMO you can have brass that has an uneven neck and still be concentric to the bore, you can have even necks and a bullet that isn't concentric to the bore
neck clearance is important for a lot of reasons but that doesn't necessarily mean turning of necks is important.

Question - who measures necks once the brass has been fired and sized many times

John T
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Re: NECK CLERANCE - IS IT IMPORTANT?

#11 Postby John T » Thu Mar 14, 2019 11:18 pm

Buffalo boys don't mind rough necks and take them as they please. Recon turning is for tossers, but insist that the hole is always the same. Some don't even wash!

If you see a box with dirty, shabby cases, it is likely you have encountered a buffalo boy. Beast advice, turn away.

bruce moulds
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Re: NECK CLERANCE - IS IT IMPORTANT?

#12 Postby bruce moulds » Fri Mar 15, 2019 5:55 am

well now we have that point cleared up, there only remains one question.
do they pick their noses, scratch their nuts, and dribble in public?
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

bruce moulds
Posts: 2530
Joined: Sun Jun 19, 2005 4:07 pm

Re: NECK CLERANCE - IS IT IMPORTANT?

#13 Postby bruce moulds » Fri Mar 15, 2019 6:53 am

getting back to artillery accuracy
during the Vietnam war, the Vietnamese were shelling the kay sarn (spelling?) base from 30 miles away in laos.
once they had the base dialled in, they started taking out individual targets like the ammo dump and the airstrip.
this was so effective that sufficient supplies could not be brought in, as only helicopters could get in.
the americans were on 1/2 rations, and had hardly any ammo, and came close to being wiped out.
American artillery did no have the range of the Chinese made enemy guns to answer the fire.
those Chinese made guns must have had fairly new barrels!
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

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

Re: NECK CLERANCE - IS IT IMPORTANT?

#14 Postby bruce moulds » Fri Mar 15, 2019 7:26 am

john t,
your description of buffalo boys raises another question.
where do buffalo boys stand on the spectrum with grunter hunters?
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

KHGS
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Re: NECK CLERANCE - IS IT IMPORTANT?

#15 Postby KHGS » Fri Mar 15, 2019 7:49 am

wsftr wrote:Perhaps it went like this.....

In the beginning there was brass and it shot well
one day a shooter said let there be better precision and so turned necks.
there was better precision, then there were split necks
so the shooter said give me less clearance between the turned necks and the chamber and there was still better precision so the shooter said turned necks shoot better and my un-annealed brass no longer splits.

Then there was a buffalo boy and he said - give me modern brass with good tolerances and a larger clearance to fit my unturned necks. Buffalo boy annealed this brass and shot it. Buffalo boy won matches and trophies. Buffalo boy said the new brass is good and the necks don't split, buffalo boy drank beer instead of turning necks.

Ever since there have been religious discussions to turn or not turn brass necks!

IMO you can have brass that has an uneven neck and still be concentric to the bore, you can have even necks and a bullet that isn't concentric to the bore
neck clearance is important for a lot of reasons but that doesn't necessarily mean turning of necks is important.

Question - who measures necks once the brass has been fired and sized many times


I'm a Buffalo Boy!!!!! =D> =D> =D> =D> =D> =D>
Keith H.


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