The Hornady comparator tool is okay, but it isn't easy to get the best readings on a VLD, or one compounded with a thin jacket with the added difficulty of a compression load.
The diameter of that tooling hole has a very slight chamfer to break the edge, otherwise it would be just a sharp edge. Either way, you already noticed how a soft, shallow, curved-tapered surface, can have variation when it meets that edge with variable pressure and friction.
There are some real challenges to mechanical inspections when it comes to contact pressure on gage anvils. We can make them out of carbide when we want to, but even then the parts we are measuring might be soft enough to cause variations in a Gage R&R test.
If you made a dummy bullet out of hardened steel, and passed the Hornady comparator gage around a room full of experienced technicians, you would still get variations that would cause concern. That tool's edge hits a shallow taper and the friction and gage pressure create variations in the readings which are bigger than the ones you would get from a tangent ogive.
This is just the nature of asking a broken edge in a hole to gage a shallow taper that is soft while using variable pressure.
Now add the challenge of a thin jacketed hunting bullet and the variations would grown.
But, we are not done with adding to the difficulty column when we remember that compressed loads can cause actual seating depth difficulties.
So we have combined the concepts that compressed powder can create bullet seating issues if taken too far, with the difficulty of the VLD angles, and added the thin jacket issues. It is a trifecta of variations. (I tell rookies to pick two, but not to try all three.)
With that said, your VLD seating stem needs to have a good contact area with that bullet type and shape to begin with, or you can distort the thin jacket. The seating depth variations can be real with a VLD.
Next, your gage pressure needs to become very consistent or you will just frustrate yourself when you try to measure these.
From there, if you are still having difficulty, you may want to consider the need of a custom comparator tool so that the surface of the tool that applies pressure to the jacket has a much wider contact area similar to the way they use a custom VLD stem for the seaters.. You can either sacrifice one of the Hornady tools, or you make it yourself. It takes some skill to match the angle, but if you can get the sharp edge to become an area contact, you will reduce the variations in the gage contact friction.
Or, try to avoid thin jacket VLD hunting bullets combined with compression loads unless you are willing and prepared to put up with the seating depth issues.
Now a comment that you didn't ask for, but I'll add it in anyway.
Since you are using a hunting bullet, I will assume you are hunting with something that doesn't resemble a Palma rig.
I have seen those shot in tight chambered custom hunting barrels and do well, I have also seen folks try and shoot them in factory chambers and not do so well. So, if your chamber is like a Palma Match chamber, you will get a return for your trouble. If it is not, I would lean more towards a tangent ogive design. YMMV
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