Neck clearence on a Match Reamer

[gunaddict]

What is your preference on neck diameter with a loaded round? 3 or 4 thousandths? This is for a no turn neck reamer. Thanks

 

[FearNoWind]

I went .002 over Sammi specs. for my .284.

 

[J E Custom]

What is your preference on neck diameter with a loaded round? 3 or 4 thousandths? This is for a no turn neck reamer. Thanks

.003 is the minimum in my opinion and .004 to .006 is preferred if you don't want to turn the necks.

.008 is used on dangerous game rifles so that chambering is not ever an issue.

Below .003 will normally cause excessive pressure.

J E CUSTOM

 

[sable tireur]

Neck clearence on a Match Reamer

The term 'Match' in conjunction with reamer making has changed definitions over the years. I questioned Dave Kiff about his labeling some reamers as 'Match' and his response was, 'any reamers which had specifications outside of SAAMI/CIP spec were labeled 'Match" unless there was a specific name with known dimensions attached to a particular reamer.' The Diego XYZ Super Duper Atom Smasher.

None of the rifles I've built have used more than 0.004" for neck clearance including those used for Dangerous Game.

Below .003 will normally cause excessive pressure.

This is simply not true unless there are extenuating circumstances. Most of us have been using 0.002" clearance for the last 3 decades that I can think of and none of us have experienced 'excessive pressure' given normal circumstances. All that's required is enough diameter for the case neck to expand in order to release the bullet. On the other hand, everyone is entitled to an opinion about how they want to do their work.

Regards.

ADDED:

CIP, SAAMI and other specifications allow manufacturers to make cartridges and to cut rifle chambers that conform to rigid specifications. The specifications for chambers set a minimum size with an upwards tolerance. The specifications for cartridges set a maximum size with a downwards tolerance. This is to ensure that the smallest chamber for a given cartridge, will always accept the largest allowed cartridge. The manufacturers of reloading dies also follow these specifications.

When the smallest allowed cartridge is fired from the largest allowed chamber, accuracy will not be good. The critical dimensions for accuracy are the freebore and neck areas.

The maximum allowed difference will allow a clearance of 0.060 mm (2.4 mil)(0.0024") The closer to zero clearance one goes, the better the alignment will be and the easier accuracy will become.


When the cartridge is fired, any clearance between the cartridge neck and the wall of the chamber will become the clearance between the inside of the case neck and the bullet. The case expands away from the bullet until it contacts the chamber wall, before the bullet has moved much.

The more clearance there is between the case and the bullet, the more the long axis of the bullet can turn away from the centerline of the barrel. This causes the bullet to enter the rifling at different angles from shot to shot and results in different points of impact.

 

[Edd]

Unless you pick a piece of brass that you think is going to be the largest ever encountered, I think setting the neck clearance at .002" for someone who isn't going to neck turn is a poor practice. I would never accept that from someone chambering a barrel of mine.

 

[FearNoWind]

... All that's required is enough diameter for the case neck to expand in order to release the bullet. ...

Well, that's certainly technically correct. My own decision to open up the neck region of the chamber just slightly over SAMMI specs. on my .284 was to eliminate entirely any need for case neck turning.

 

[sable tireur]

Unless you pick a piece of brass that you think is going to be the largest ever encountered, I think setting the neck clearance at .002" for someone who isn't going to neck turn is a poor practice. I would never accept that from someone chambering a barrel of mine.

This has always been a part of the discussion between gunsmith and client, which is had prior to starting any work, especially nowadays when there is the potential for any brass maker to change the neck wall thickness on a whim without telling anyone (Lapua). The gunsmiths I know and trust would never 'assume' that they knew what the client needed or wanted for a chamber without first having a detailed discussion regarding brass and bullets.

As I stated, everyone has their own opinion on how things should work. But there is a base line for many of the decisions as established by SAAMI/CIP. No one says you have to agree.

Regards.

 

[gunaddict]

I appreciate the feedback. This reamer I am going to order is for a hunting rifle only.

 

[dok7mm]

Interesting discussion! I normally acquire the best brass I can, prior to deciding on reamer selection. After a lot of neck measuring, I have a good idea of what chamber neck dimension I want in my reamer. I nearly always pick a no-turn or tight neck and turn my case necks for the clearance I want. I often start at .003" clearance, but end up at .004" for long range hunting calibers.

I recently used Norma 280 brass necked down to 6.5 Sherman. After fire forming, I only had .001"+ of clearance. I tried .003" clearance first and it was ok, but really shoots well with .004". Just my observation.

 

[gunaddict]

As stated before I don't want to turn necks!!!!!!

 

[J E Custom]

The term 'Match' in conjunction with reamer making has changed definitions over the years. I questioned Dave Kiff about his labeling some reamers as 'Match' and his response was, 'any reamers which had specifications outside of SAAMI/CIP spec were labeled 'Match" unless there was a specific name with known dimensions attached to a particular reamer.' The Diego XYZ Super Duper Atom Smasher.

None of the rifles I've built have used more than 0.004" for neck clearance including those used for Dangerous Game.



This is simply not true unless there are extenuating circumstances. Most of us have been using 0.002" clearance for the last 3 decades that I can think of and none of us have experienced 'excessive pressure' given normal circumstances. All that's required is enough diameter for the case neck to expand in order to release the bullet. On the other hand, everyone is entitled to an opinion about how they want to do their work.

Regards.

ADDED:

CIP, SAAMI and other specifications allow manufacturers to make cartridges and to cut rifle chambers that conform to rigid specifications. The specifications for chambers set a minimum size with an upwards tolerance. The specifications for cartridges set a maximum size with a downwards tolerance. This is to ensure that the smallest chamber for a given cartridge, will always accept the largest allowed cartridge. The manufacturers of reloading dies also follow these specifications.

When the smallest allowed cartridge is fired from the largest allowed chamber, accuracy will not be good. The critical dimensions for accuracy are the freebore and neck areas.

The maximum allowed difference will allow a clearance of 0.060 mm (2.4 mil)(0.0024") The closer to zero clearance one goes, the better the alignment will be and the easier accuracy will become.


When the cartridge is fired, any clearance between the cartridge neck and the wall of the chamber will become the clearance between the inside of the case neck and the bullet. The case expands away from the bullet until it contacts the chamber wall, before the bullet has moved much.

The more clearance there is between the case and the bullet, the more the long axis of the bullet can turn away from the centerline of the barrel. This causes the bullet to enter the rifling at different angles from shot to shot and results in different points of impact.

The term 'Match' in conjunction with reamer making has changed definitions over the years. I questioned Dave Kiff about his labeling some reamers as 'Match' and his response was, 'any reamers which had specifications outside of SAAMI/CIP spec were labeled 'Match" unless there was a specific name with known dimensions attached to a particular reamer.' The Diego XYZ Super Duper Atom Smasher.

None of the rifles I've built have used more than 0.004" for neck clearance including those used for Dangerous Game.



This is simply not true unless there are extenuating circumstances. Most of us have been using 0.002" clearance for the last 3 decades that I can think of and none of us have experienced 'excessive pressure' given normal circumstances. All that's required is enough diameter for the case neck to expand in order to release the bullet. On the other hand, everyone is entitled to an opinion about how they want to do their work.

Regards.

ADDED:

CIP, SAAMI and other specifications allow manufacturers to make cartridges and to cut rifle chambers that conform to rigid specifications. The specifications for chambers set a minimum size with an upwards tolerance. The specifications for cartridges set a maximum size with a downwards tolerance. This is to ensure that the smallest chamber for a given cartridge, will always accept the largest allowed cartridge. The manufacturers of reloading dies also follow these specifications.

When the smallest allowed cartridge is fired from the largest allowed chamber, accuracy will not be good. The critical dimensions for accuracy are the freebore and neck areas.

The maximum allowed difference will allow a clearance of 0.060 mm (2.4 mil)(0.0024") The closer to zero clearance one goes, the better the alignment will be and the easier accuracy will become.


When the cartridge is fired, any clearance between the cartridge neck and the wall of the chamber will become the clearance between the inside of the case neck and the bullet. The case expands away from the bullet until it contacts the chamber wall, before the bullet has moved much.

The more clearance there is between the case and the bullet, the more the long axis of the bullet can turn away from the centerline of the barrel. This causes the bullet to enter the rifling at different angles from shot to shot and results in different points of impact.

Not to start an argument. But this has been a misconception for many years and the only time less clearance than .003 should be used is if the neck is turned for a perfect chamber fit and loaded without any sizing. (This used to be common practice for bench rest shooters) all loads were less than maximum so pressure was not an issue.

Using the neck to align a cartridge in a magnum cartridge is dangerous
without reducing the powder charge, and also unless the neck is the same size as the chamber, alignment does not exist because it ether fits or it doesn't. proper sizing of the case body and the shoulder will align the cartridge and no mater how much clearance the neck has, it will be aligned.

A well known gunsmith on this site discovered the problems with to little neck clearance in his pursuit for accuracy and velocity, and had to go back and increase this clearance on many of his rifles because of excessive pressure.

There is no way that anyone can guaranty that a non turned neck will have perfect clearance all the way around if the neck has been chambered .001 to .002 thousandths larger than a loaded round.
Most unturned brass cases have .001 to .003 thousandth differences in thickness from one side to another, hence the reason that .003 to .004
thousandths should be the minimum clearance. .004 thousandths larger neck chamber stills only gives you .002 thousandths per side. so
I will always recommend .004 thousandths larger than the loaded round
to stay out of trouble.

There used to be many things that were normal when pressures were less than 55,000 PSI but with pressures reaching 70,000 psi and in some cartridges more the rules have changed and need to be addressed.

PS: on dangerous game rifles more clearance is needed to assure that the second round will chamber even in a dirty or fouled chamber so you don't end up that green stuff between the elephants toes. the best group I have ever shot was .034 thousandths with a 416 and a 400 grain bullet with a total neck clearance of .008 ( .004 thousandths per side)

Just my opinion and experience

J E CUSTOM

 

[dok7mm]

Unless I misread, you stated you were getting a no-turn reamer, not that you didn't want to turn necks. Excuse me!

 

[sable tireur]

Not to start an argument. But this has been a misconception for many years and the only time less clearance than .003 should be used is if the neck is turned for a perfect chamber fit and loaded without any sizing. (This used to be common practice for bench rest shooters) all loads were less than maximum so pressure was not an issue.

No argument is intended. But stating that I suffer from a misconception is a falsehood plain and simple. Your experience or lack thereof possibly points to your background or misunderstanding of what is being stated. The shortest explanation revolves around experience and a desire to provide the best possible system for a client. My system has worked for a seriously long period of time and by sheer numbers, involving both extreme accuracy rifles and rifles meant for use on dangerous game. Neither has ever failed to provide for a client.

There has been and always will be disagreements regarding the technical and mechanical nature of firearms. We have seen the gamut of ideas change over the period of time for both aspects when efforts have been exerted to further our knowledge and understanding. It's bound to happen as we expand our realm of understanding.

So we disagree and there's nothing wrong with that. It always makes for a good discussion.

Regards.

 

[J E Custom]

No argument is intended. But stating that I suffer from a misconception is a falsehood plain and simple. Your experience or lack thereof possibly points to your background or misunderstanding of what is being stated. The shortest explanation revolves around experience and a desire to provide the best possible system for a client. My system has worked for a seriously long period of time and by sheer numbers, involving both extreme accuracy rifles and rifles meant for use on dangerous game. Neither has ever failed to provide for a client.

There has been and always will be disagreements regarding the technical and mechanical nature of firearms. We have seen the gamut of ideas change over the period of time for both aspects when efforts have been exerted to further our knowledge and understanding. It's bound to happen as we expand our realm of understanding.

So we disagree and there's nothing wrong with that. It always makes for a good discussion.

Regards.

I was talking in general about the misconceptions not anyone specific But that is about the most eloquent rebuttal I have ever had.

I never try to figure out what experience a person has nor does anyone know what experience I have. I only render my opinion based on the experiences I have had and if they don't agree with others, so be it.

I also try to avoid any modifications to the SAMMI specifications that could cause an inexperienced shooter or re-loader problems. I don't assume that all shooters can deal with tight tolerances or tricky loading practices. Probably only 10% of the population understand the cause and effects of some of these changes and know how to deal with them
to get there desired outcome.

Also the OP said he wanted a no turn neck diameter which changes the requirements in my opinion.

And as you said If we disagree, So what. Ideally, we can give some sound advice and help the OP to come to a decision on what he wants
and the problems with what he wants/needs to do.

J E CUSTOM