Drop a go gauge into a cartridge gauge, this is not what I expected

C

Clark

New member
I thought the go gauge would come up level with the top of the case gauge. I was wrong. I looked into it further.

I thought that in SAAMI drawings tolerance there would be a range for cartridges and a range for chambers with no overlap, so there was guaranteed clearance.
I was wrong. It is up to a 0.004" interference fit.

I thought the two levels on top of the case gauge would represent the min and max lengths for a cartridge.
I was wrong. It is from the longest to ~~halfway to the shortest the cartridge can be.

I am now thinking I should keep on headspacing rifles so the bolt just closes on the go gauge.
But I will be using the case gauge only for relative measurements, not as absolute, to measure brass, to adjust sizer dies.

*************************************

The 243 cartridge, per SAAMI is 1.634 -0.007"
The 243 chamber, per SAAMI, is 1.630 +0.010"
---------------
0.0040" overlap

243-308 1.630 go gauge dropped into a
243 Wilson case gauge
Down 0.004" from the top of 0.0045" twin levels

*************************************************

The 6mm cartridge per SAAMI is 1.7807 -0.0070"
The 6mm chamber per SAAMI is 1.7767 +0.0100"
-----------
0.0040" overlap

6mm Rem go Manson dropped into a
6mm Remington Wilson case gauge
Down 0.003" from the top of 0.0045" twin levels

*******************************************

The 270 cartridge per SAAMI is 2.0526 -.0070"
The 270 chamber per SAAMI is 2.0487 +0.0100"
------------------
0.0039" overlap

270 30-06 25-06 Forster go gauge 2.0487 dropped in a
Forster-Appelt 270 Win case gauge
Down 0.0035" from the top of 0.0055" twin levels

************************************************

The 30-06 cartridge per SAAMI is 2.0526 -.0070"
The 30-06 chamber per SAAMI is 2.0487 +0.0100"
------------------
0.0039" overlap

270 30-06 25-06 Forster go gauge 2.0487 dropped in a
30-06 Wilson case gauge
Down 0.0055" from the top of 0.0050" twin levels
 

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Back in the day, when I was getting tooled up to do a better job of reloading for several calibers, I looked at the cost of having a case gauge for each, and how awkward they are to use to come up with actual measurements and I decided that the Stoney Point caliper attachment, with the various sleeves would be a lot more economical and convenient. IMO that was a good move.
 
nothing new,
just new when you discovered it,
been that way for a long time.
 
OK, dumb question of the day, what's a case gauge? More specifically, "what is it for??"

I think I have some in my graveyard, some of the Wilson ones seem bloody hard and have a .003-.004ish slot or groove milled acros't the face??? What is the supposed function of such an animal? Why do they exist?
 
The 223 case SAAMI drawing is 1.4666 -.0070
The chamber is 1.4636 + 0.0100
0.0030 overlap in a range of 0.0140"

Watching this video by Wilson, they say the 223 case gauge measures the SAAMI min and max for a cartridge with 0.005" groove.
This does not make sense.
That would require a 0.0070" groove on top.
Then Wilson puts a fired case in the case gauge as says it sticks up, so the rifle must have a chamber that exceeds SAAMI specs.
Makes less sense. That would require a 0.0140" groove on top, not a 0.0050" groove.
Maybe I am being too fussy about numbers adding up and words having definitions.

 
Use the Hornady comparator to measure. Place a fired case in the Wilson gage. The FL sized brass should be at the same level or slightly lower. Spring back of the fired brass comes into play here.
Casegage012Aa.jpg
 
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Two tools used for entirely different purposes. One measures the chamber depth from the bolt face and the other measures cartridge case length. The chamber and cartridge have different specs for a reason, thus requiring different means of measurements, I've fought this battle before with customers.
 
Posts:199
The 223 case SAAMI drawing is 1.4666 -.0070
The chamber is 1.4636 + 0.0100
0.0030 overlap in a range of 0.0140"

Watching this video by Wilson, they say the 223 case gauge measures the SAAMI min and max for a cartridge with 0.005" groove.
This does not make sense.
That would require a 0.0070" groove on top.
Then Wilson puts a fired case in the case gauge as says it sticks up, so the rifle must have a chamber that exceeds SAAMI specs.
Makes less sense. That would require a 0.0140" groove on top, not a 0.0050" groove.
Maybe I am being too fussy about numbers adding up and words having definitions.
Click to expand...

If a reloader and or smith knew how to make gages the gages they purchase would not seem so complicated. I use a straight edge and feeler gage with the Wilson case gage. I have also used a flat surface and a feeler gage. I do not care how Wilson made the gage, I do not care if they are accurate. When I want to determine how accurate a tools is I use a standard. If I am not happy with my standards I will make one. There was a time I wondered about what it was that causes reloaders to get into mortal combat when only finding fault in a tool or another human. When it comes to measuring my tools are limited; my tools can only measure from and to. Many years ago I thought smiths and reloaders had an infatuation with head space. Head space this and head space that, so I piled up a few tools that had nothing to do with the length of the chamber and adapted them to measure the length of the chamber from the shoulder to the bolt face. I then modified a go-gage to measure the length of a chamber from go to infinity. We all know there is no practice application for a gage that measures the length of a chamber that goes beyond a field reject length chamber when measuring from the shoulder to the bolt face but to make a point I made the effort.

F. Guffey
 
F. Guffey said:
..........We all know there is no practice application for a gage that measures the length of a chamber that goes beyond .........etc, etc....
F. Guffey
Click to expand...

You make some truly odd and unfounded assumptions Mr Guffey.

And we all find different things to be useful....

My lens is not yours Mr Guffey

and visey-varsey

al
 
John Kielly said:
Am I correct in my recollection that a pri,er can be .004 thicker than a primer pocket is deep?
Click to expand...

If by 'thicker' you mean taller....my recollection agrees.

I've found pri,ers that never touch'd the bottom o' the 'ole and those which stood tall and proud requiring crush just to get down....although most often if the difference is much over a thou it's the brass' fault ;)
 
243winxb said:
The Hornady comparator or Wilson gage may have no value in checking head to datum measurement of fired brass from some auto gas guns. http://www.hornady.com/ammunition/superformance-in-gas-operated-firearms
Click to expand...

And then there is the 'repeat after me' philosophy of reloading: goes something like the case expands and locks onto the chamber, if the case head is not against the bolt face the case will stretch between the case head and case body. Question: If the case has not finished firing how is the case removed from the chamber before pressure drops. I am thinking things happen faster than a reloader can think. My philosophy suggest the chamber in that machine gun is generous, when fired the case expands more than the reloader can handle. I have no problem sizing machine gun fired 308 cases, when the going gets tuff I use a forming die, and then I have no infatuation with case lube. When the case wins I use a no name lube; there are cases that can be sized with any lube; I do have trouble making Imperial and Dillon in a can or bottle look good when trying to size cases that have been hammered with heavy loads.

F. Guffey
 
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