On the tip or on the Butt?

[drone]

Here's a query that I asked Lee Customer Services and the answer wasn't clear.

gage 2.jpg

The image shows the end of the Lee cartridge length gage, I have several of these, 308 win, 30/30, 223, 38 sp and 357 mag. On some of them the point B of the pin is proud of the face of the base of the cartridge and on others it isn't, this is when the gage is pushed fully home when the case is held in my hand.
Point A is the the end of the main section.
Is the length of the case dictated by point B or is it dependent on Point A?
I've run all my 308 cases through the trimmer with a drill and that point gets hot, as you can see it's blued from rubbing against the anvil in the case holder.
When trimmed back using point B, the cases measure 50.89mm, a midge's dick under 2.004".

[GasGuzzler]

A

B just centers on the flash hole.

I think.

I used Lee's system about 11 minutes before I went with a better design from a different company.

[RBHarter]

Their system works by making a dead stop . The length from the outside of the case rim/head face to the cutter face is set by the insert rod through the case , flash hole , and stoping against holder set bolt .

In design it's absolute precision, absolutely 100% repeatable .
In practice it is close enough per cartridge, it doesn't allow for wear or long/short chambers without mods .