chamber length vs. max case length

[atlatl]

Recently I measured the chamber length of a rifle I had built. Using a Sinclair Chamber Length gauge and modified case, I get a measurement 0.058" longer than the maximum case length of the cartridge, ie max SAAMI case length is 2.233 and the chamber in my rifle would allow a case length of 2.291.

Head space in this chamber is perfect. I believe the the gunsmith cut the neck separately with a throating/necking reamer and ran it too deep.

I suspect this discrepancy between cartridge case length and chamber neck length does nothing to promote accuracy.

What is the proper relation between case length and chamber length?- Thank you

 

[Jay Christopherson]

I think maybe your measurement is off. I have a hard time believing the case allowance of your chamber is nearly .060" longer than spec and I've never heard of a gunsmith cutting the "neck" longer. Throating, sure, but that has no relation to the neck. I've never heard of a "neck reamer" either, but that doesn't mean it doesn't exist I guess. I don't know what purpose it would serve.

If you measure a few more times and your measurement is still consistently longer than you expect, I'd probably try casting the chamber with Cerro-safe.

 

[Erik Cortina]

Jay, if you have a tight neck reamer, you can use a neck reamer to make it a no turn neck.

So, if gunsmith did it separately, there is a possibility that he may have cut it too deep. However, surprise, surprise, some reamers do not match reamer prints!

 

[Eddie Harren]

+1 for reamers not matching prints.

 

[Jay Christopherson]

<snip>
Jay, if you have a tight neck reamer, you can use a neck reamer to make it a no turn neck.

So, if gunsmith did it separately, there is a possibility that he may have cut it too deep.
</snip>

I'll be darned. Learned something new.

 

[atlatl]

I am quite certain of the measurement. I also am fairly certain the neck was cut in a separate step as I specified a .276 neck and the smith told me he had to obtain a neck reamer to do so.

The question remains- what is the proper relationship between max case length and the end of the chamber's neck? Ideally, is the end of the neck just a few thousands longer than maximum allowable case length?

I ask as I intend to have the barrel set back slightly and the chamber recut. I appreciate any advise on how best to correct it.

Thank you.

 

[Erik Cortina]

I am quite certain of the measurement. I also am fairly certain the neck was cut in a separate step as I specified a .276 neck and the smith told me he had to obtain a neck reamer to do so.

The question remains- what is the proper relationship between max case length and the end of the chamber's neck? Ideally, is the end of the neck just a few thousands longer than maximum allowable case length?

I ask as I intend to have the barrel set back slightly and the chamber recut. I appreciate any advise on how best to correct it.

Thank you.

.010" to .020" is ideal.

 

[atlatl]

Thank you.