So in his video how is he measuring primer depth ?? Is he not using calipers ? So if calipers are not accurate then how is this video accurate ?? Just asking.
Im not an expert but i do have access to a parts catalogue, so will make a couple comments.
It seems likely the only way to measure this properly is with class .0001 dial indicator. And one that has accuracy in line with its resolution...
IE typically an expensive specialty item $
You're mitutoyo digital pn is the high end 543-79X series, at least $250, not the standard 543-78x which is $150.
Also importantly, most non-digital dial gauges with this precision are severely travel limited ... 10x more precision with 1/10th the travel range.
This means they typically lack the range to measure a large primer pocket's depth to max spec...to check its uniformity. An accurised 1 inch form factor indicator, restricted to .10 inches cant measure .130 for example.
Most high precision dial gauges are ranging only .025 or .050
If you want an indicator to do both, try to find .5 range and .0005 accuracy, so the .001 scale actually means something.
These are uncommon units and typically cost $$$. Look for a mitutoyu like 2356s-10 or $200 or possibly 2415s for $150.
A 'generic' model 1 in travel dial indicator even in a high quality nameplate is typically only -/+ .001 accurate, not good enough.
Lastly, the measurement of the primer pocket is subject to measurement error if the tip (contact point) isn't the correct size or shape.
See mitutoyo pn 7832 for a selection of contact point shape and sizes. Probably want a 5mm flat point [edit: 2mm carbide tip #137257]
This also would mean you need fixtures capable of holding the indicator and test piece at 90 degree angles correctly, etc.
Someone please correct me if i am wrong...