TECH TIP: Case Gauge -vs- Min Dimension Gauge

Wondering what the difference is between a standard “Case Gage” and a “Min-Chamber Gage”? That’s exactly what we’ll cover in this story!

Wilson Case Gage

A standard case gage from Wilson Tools and Gages (LE Wilson) is used for two things. First, you can view the back of the case gauge to check headspace (sizer die setup):

The back of the case rim should fall between the two steps as shown above. If the case rim is below the bottom step, you’ve over-sized the case. If the back of the case rim protrudes beyond the upper step, you need to size more for proper chambering.

On the other side of the gage you can check for trim length:

If the case mouth protrudes beyond the upper step,  you need to trim. If the case mouth is below the lower step, you may have over-trimmed (based on your own preferences). Note: This check is done by looking “up” at the bottom of the gage with the cartridge pointed “bullet down”.

Wilson Min-Dimension Gage

The Min-Dimension Gage from Wilson Tools and Gages is used to check minimum headspace, and cartridge overall length. Here you can see the check for minimum headspace:

Here, if the case rim protrudes above the back face of the gage, your cartridge won’t chamber in a SAAMI minimum-spec chamber, but may chamber in a chamber cut to longer depth (SAAMI maximum for example).

Flipping the gage over, we can slip the gage over a cartridge to check for Cartridge Overall Length (COL):

If the tip of the bullet is not protruding from the end of the gage, the cartridge is at or below maximum COL for that cartridge spec:

Ideally you’ll have one of each of these gages for the cartridges you load!

Get Yours

Wilson Gages are available at Midsouth Shooters Supply! Here are the individual product categories:

Wilson Case Gages at Midsouth

Wilson Minimum Dimension Gages at Midsouth

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Thanks,
Gavin

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