Chamber shoulder and case shoulder gauge for .303?

[Parashooter]

. . . We should think of the case being pushed forward rather than the base being pushed back.

I have seen this idea with fair frequency and eventually decided to test it -



I believe that when a rimmed cartridge is fired with generous shoulder clearance the case expands outward to fill the chamber and there is little or no elongation (stretch) due to brass being "pushed forward". I'd be delighted to hear details of any tests that either confirm or refute what I've concluded from my little experiment.

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Ed, I apologize for the offense. It was not my intent. I have great confidence in your measurements and observations about the .303 cases you've examined and shown us. That they differ from what I've experienced tells me there has been some significant variation in production - enough that I question the value of any generalization based on what either of us have observed in a variety of specimens.

To be specific, I question assertions that -

• US makers are routinely loading .303's to reduced pressure.
• Shoulder clearance is a defect in (new) rimmed cases.
• There is a qualitative difference in the metal US makers employ for .303 cases.

All of these may be valid points. I'm just saying that I haven't yet seen any conclusive evidence to support them and my experience differs. Please don't stay angry.

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[ireload2]

I have seen this idea with fair frequency and eventually decided to test it -



I believe that when a rimmed cartridge is fired with generous shoulder clearance the case expands outward to fill the chamber and there is little or no elongation (stretch) due to brass being "pushed forward". I'd be delighted to hear details of any tests that either confirm or refute what I've concluded from my little experiment.

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Ed, I apologize for the offense. It was not my intent. I have great confidence in your measurements and observations about the .303 cases you've examined and shown us. That they differ from what I've experienced tells me there has been some significant variation in production - enough that I question the value of any generalization based on what either of us have observed in a variety of specimens.

To be specific, I question assertions that -

• US makers are routinely loading .303's to reduced pressure.
• Shoulder clearance is a defect in (new) rimmed cases.
• There is a qualitative difference in the metal US makers employ for .303 cases.

All of these may be valid points. I'm just saying that I haven't yet seen any conclusive evidence to support them and my experience differs. Please don't stay angry.

Para,

I have a similar observation. I have formed .303 brass from once fired .30-40 Krag brass. There is not really much to it other than trimming to length and resizing to retain a bullet. The Krag shoulder is far below the .303 shoulder.
It seems many hand loaders can only think of brass as stretching longitudinally.
What I have observed is that brass tends to stretch radially first then longitudinally. In the case of the Krag brass it had a different surface color at the shoulder than it did over the neck. When fired in the .303 chamber the case merely expand radially. A new shoulder is formed at the proper location in the .303 chamber. The color tone and previous sizing marks on the Krag shoulder remain where they were, they are just expanded in diameter.

Once fired Krag case on the left. Note color of shoulder.
The case on the right was trimed to .303 length and fired in .303 #4MK1.
Note color band on the should is still in the same location.

This from my Frankenstein box of .303 brass that includes reformed .444 Marlin, .30-40 Krag, WW Super, Western Super Speed, two different R-P headstamps and Herter's.



EDG