Chamber Neck Diameter
- Thread starter Edd
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shortgrass
Well-Known Member
It's a non-issue.
aushunter1
Well-Known Member
Cases are made to SAAMI specs but of course there are variations of things like brass thickness in different areas.
Sounds like you are referring to what I would actually call excess & uneven brass thickness in the outside diameter of the case neck over a taper.
This is why people turn their case necks when they want a more precise neck tension.
If you resize correctly & trim to length then you won't have any chambering issues
Sounds like you are referring to what I would actually call excess & uneven brass thickness in the outside diameter of the case neck over a taper.
This is why people turn their case necks when they want a more precise neck tension.
If you resize correctly & trim to length then you won't have any chambering issues
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The question was not about brass, it was about the chamber.
J E Custom
Well-Known Member
Chambers have the neck part of the chamber tapered for extraction advantages. The cartridge case will be straight when sized and while loaded for uniform grip/tension on the bullet. Only when fired will the cartridge take on this .001 thousandths taper. the fact that it only occurs when the case has been fired has no effect on accuracy or anything because the neck will be .003 or .004 larger than the bullet after firing.
Just like un-fired brass, turned brass will not have a taper until it is fired in the chamber. Even straight sided cases (Like the 45/70 and others) have a slight taper on the outside for extraction. If the neck was perfectly straight, potentially it could be mechanically bound up if debris was left in the chamber from previous firings but the .001 thousandths taper all but eliminates this phenomena.
The reamer has this same amount of taper in it in order to cut the chamber the same as the Spec. As Shortgrass said "No Problem"
J E CUSTOM
Just like un-fired brass, turned brass will not have a taper until it is fired in the chamber. Even straight sided cases (Like the 45/70 and others) have a slight taper on the outside for extraction. If the neck was perfectly straight, potentially it could be mechanically bound up if debris was left in the chamber from previous firings but the .001 thousandths taper all but eliminates this phenomena.
The reamer has this same amount of taper in it in order to cut the chamber the same as the Spec. As Shortgrass said "No Problem"
J E CUSTOM
aushunter1
Well-Known Member
bigngreen
Well-Known Member
I don't know anyone who ordered reamers with the neck taper in them on modern cartridge designs.
How much neck clearance are you putting in your chambers?
bigngreen
Well-Known Member
shortgrass
Well-Known Member
It depends..... Large hunting cartridges are usually given more clearance than a BR chamber. I like to run about .003 on my own, personal varmint rifles. My 30/06 and .338 Win Mag (and my 300 Win Mag) have .004-005. The reamer makers give themselves .0005 tolerance for custom grinding. I think about all 'gunsmith' chambering reamers come with the neck portion straight, and not tapered. As I said, straight is a non-issue.
Yesterday, I was ordering a reamer. Based off the SAAMI reamer print I have and the brass I have, I was needing to change the neck diameter. I was considering ordering it with a straight neck but I went ahead and ordered it with a .001" taper.
J E Custom
Well-Known Member
You did good In my opinion.
.001 Thousandths neck taper Is normal for most SAMMI chambers. Neck clearance When fired is ,003+ depending on the use and size of the cartridge. some dangerous game cartridges have as much as .008 to guaranty that the bullet is released freely to manage pressure. Neck clearance a totally different purpose and has nothing to do with the neck taper purpose Ed is asking about.
When wildcatting, I always ask for the .001 neck taper because it doesn't have any effect on anything but extraction, And with the straightening/Reducing the case wall taper of the case walls it can do nothing but help.
J E CUSTOM
ShtrRdy
Well-Known Member
I was looking at the SAAMI drawing for the 6mm Creedmoor and the chamber neck doesn't have any taper. Most other chambers have the 0.001" taper as has been mentioned.
J E Custom
Well-Known Member
That's because they consider it a wildcat or a 6mm/6.5 CM. They may change it to a standard SAMMI cartridge, but they will probably leave it like it is with no neck taper.
Many of the long term wildcats that have proven themselves remain as is in SAMMI.
J E CUSTOM
