FFB Primer Seating Depth Measuring Fixture


In stock



For too long now it’s been too difficult to check primer seating depth.  Our simple fixture conveniently mounts to any bench using 1/4″ fasteners.  Once the indicator is installed and zeroed, primer pocket depth can be check in just a second or two.  No more guessing.  No more imprecision.  Know whether your press is repeating the primer insertion depth.

Depending on your accuracy needs, the following gauges are known to work.
– Starrett 25-211J (0-0.025″ range, 0.0001″ accuracy, street price March 2023 of ~$300.00)
– Mitutoyo 1507A (0-0.125″ range, 0.0005″ accuracy, street price March 2023 of ~$110.00)

1.  Attach the fixture to the work bench using the pair of 1/4″ holes.
2.  Insert the dial indicator as shown in the product photo.  The indicator tip should protrude to about mid stroke.
3.  Snug the 6-32 screw to hold the indicator.  Do not over tighten the screw or the indicator will bind and throw off readings.  After tightening, ensure the indicator repeats to zero.  If it does not, the screw is too tight.
4.  Use a machined flat surface to push the indicator tip flush with the machined face of the gauge fixture.
5.  Loosen the bezel adjustment screw and turn the bezel to where it reads 0.0000″ when the indicator tip is flush.

Hold a primed case against the machined surface with the dial indicator.  The fixture will check small and large pistol or rifle primers.  If the needle reads counter clockwise to zero, the primer is recessed.  If the needle reads clockwise of zero, it is proud.  Typically, depending on primer brand, the range of 0.004″ to 0.007″ recessed is acceptable.  Some primers are more sensitive than others due to the detonation material used, which is why the aforementioned depth is a recommendation, not a hard number.  The depth of the primer also pre-loads the primer anvil, and will have a direct impact on the sensitivity of the firing pin strike required to detonate the primer.