How accurate is the given neck diameter with good reamer and competent gunsmith? What I mean is: If the neck is supposed to be .262, does that mean it could be .2615 up to .2625?? Mesuring the fired neck is not accurate, because of springback. I guess the only way to make an accurate determination is to cast the chamber.
Reamer accuracy
- Thread starter tenring
- Start date
tenring
Measuring a chamber neck with a chamber cast is tricky. As you know, the cast begins to change dimensions as soon as it starts to cool. I suppose if you measure the cast after the specified period of time and repeat it 3 or 4 times you can say that you have a reasonably accurate figure.
I once asked a well known reamer maker and a well known gunsmith your first question. They both gave me the same answer. If the reamer says .262", the chamber neck will be .262". Otherwise you should get a new reamer maker and gunsmith. Theoretically they are right but in the real world it seldom works out that nicely.
I would not worry about such things because you will only go nuts. If you look at a table of the ASA standards of fits between a hole and a shaft you will find tolerances of up to .0005. I'd say if you can measure the chamber neck to the nearest 1/2 thou, without using machined plugs, you are doing good. JMHO
Ray
Measuring a chamber neck with a chamber cast is tricky. As you know, the cast begins to change dimensions as soon as it starts to cool. I suppose if you measure the cast after the specified period of time and repeat it 3 or 4 times you can say that you have a reasonably accurate figure.
I once asked a well known reamer maker and a well known gunsmith your first question. They both gave me the same answer. If the reamer says .262", the chamber neck will be .262". Otherwise you should get a new reamer maker and gunsmith. Theoretically they are right but in the real world it seldom works out that nicely.
I would not worry about such things because you will only go nuts. If you look at a table of the ASA standards of fits between a hole and a shaft you will find tolerances of up to .0005. I'd say if you can measure the chamber neck to the nearest 1/2 thou, without using machined plugs, you are doing good. JMHO
Ray
Tenring:
A reamer cuts on an axis. Since it is cylindrical, if it or the material to be reamed is not coaxially and concentrically aligned it will cut a "wallered out hole", ecentric,cam or egg shaped) or over bore. I don't care if you are the best you can't manually cut a perfectly round bore. In some cases you would not want to because the barrel bore is not drilled straight. Gunsmiths and machinest do their best. In theory a properly dialed in floating reamer holder gives us about the best opertunity to cut as perfect a chamber as we can cut.
Very few factory gun makers have employees with the time, experience, and/or tooling need to cut precision chambers. Nor do they use barrels of the same quality as the available aftermarket barrels.
I had an e-mail yesterday from a man who he and his buddy both bought new " target grade factory rifles" that had necks that were .005 out of spec. I only see the problem getting worse as we don't have the journeymen in the trades any more. The engineers are not machinest.
Chamber cast/throats can be very good tools to show a gun manufacture the problem. A borescope video is another great tool. I have had manufactures send me trouble guns for investigational purposes and/or repair. some companies will pull a gun off their line for inspection purposes and send them out to an independent smith for review. Often they don't like what they hear but the bean counters run the show and don't stop the lines and correct the problems.
Rustystud
A reamer cuts on an axis. Since it is cylindrical, if it or the material to be reamed is not coaxially and concentrically aligned it will cut a "wallered out hole", ecentric,cam or egg shaped) or over bore. I don't care if you are the best you can't manually cut a perfectly round bore. In some cases you would not want to because the barrel bore is not drilled straight. Gunsmiths and machinest do their best. In theory a properly dialed in floating reamer holder gives us about the best opertunity to cut as perfect a chamber as we can cut.
Very few factory gun makers have employees with the time, experience, and/or tooling need to cut precision chambers. Nor do they use barrels of the same quality as the available aftermarket barrels.
I had an e-mail yesterday from a man who he and his buddy both bought new " target grade factory rifles" that had necks that were .005 out of spec. I only see the problem getting worse as we don't have the journeymen in the trades any more. The engineers are not machinest.
Chamber cast/throats can be very good tools to show a gun manufacture the problem. A borescope video is another great tool. I have had manufactures send me trouble guns for investigational purposes and/or repair. some companies will pull a gun off their line for inspection purposes and send them out to an independent smith for review. Often they don't like what they hear but the bean counters run the show and don't stop the lines and correct the problems.
Rustystud
And Rusty I'm sure this has happened to you too. You cut a chamber that is so damn perfect that you call your wife out to the shop to show her,as if she really cared
). And the thing won't shoot any better than average groups. Then you screw one up so bad that you hide it under the workbench and it turns out to be a hummer.
Ray
). And the thing won't shoot any better than average groups. Then you screw one up so bad that you hide it under the workbench and it turns out to be a hummer.Ray
Cheechako:
I ran my wife off about 12 years ago. She never went into my shop before she moved on. I am not a rocket scientist but once was enough. If it flies, floats or you know what, it is cheaper to rent it.
Yes, I have screwed up a barrel before and will screw up another in the future. But I don't send them out to the customer. I order them a new barrel and get it right before I send it to the customer. I am very anal as are most precision shooters. Knock on wood, I have never had a customer complain about quality work or not getting their monies worth.
Rustystud
I ran my wife off about 12 years ago. She never went into my shop before she moved on. I am not a rocket scientist but once was enough. If it flies, floats or you know what, it is cheaper to rent it.
Yes, I have screwed up a barrel before and will screw up another in the future. But I don't send them out to the customer. I order them a new barrel and get it right before I send it to the customer. I am very anal as are most precision shooters. Knock on wood, I have never had a customer complain about quality work or not getting their monies worth.
Rustystud
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