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Inconsistent BTO Measurements

Linko

Silver $$ Contributor
I would like to have a consistent measurement of my seating depth.
I use a Mitutoyo caliper with Hornady comparator tool and Sinclair insert.
I use this setup and can get just about any measurement I want by wiggling the base to ensure it is seated flat on the anvil.
Here are two examples of the same loaded round. This is a 6 Dasher with a Barts bullet

I am sure it operator affected. If I sort loaded cartridges using this caliper setup and I have them in a reloading tray and repeat the measurements I will be jumping the cartridges back and forth from short to long.Nuts!

Is a hard jam in the comparator insert a better method of doing this. Or is there a better way to measure BTO consistently?

I use the Innovative Technologies tool for shoulder bump/headspace. Rotating the cartridge on the base yields a steady measurement. I do the same with the caliper setup and it’s not consistent


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It’s likely the tools, I switched to Accuracy One comparator and realized my seating was near perfect. 95% are within .0005
This is a different method that the caliper method. Similar to the whidden tool in both measures shoulder to ogive. The caliper comparator I’m using is base to ogive. I think Bob greens is shoulder to ogive.

Interesting
 
My opinion, your expectations for a caliper measurement are a little high. I have seen an adaptation for a micrometer, but it smell like you still want a better measurement.

My goal is always to find a seating approach that is tolerant and works with my reloading tolerance. Measurement and real variations.
 
I would like to have a consistent measurement of my seating depth.
I use a Mitutoyo caliper with Hornady comparator tool and Sinclair insert.
I use this setup and can get just about any measurement I want by wiggling the base to ensure it is seated flat on the anvil.
Here are two examples of the same loaded round. This is a 6 Dasher with a Barts bullet

I am sure it operator affected. If I sort loaded cartridges using this caliper setup and I have them in a reloading tray and repeat the measurements I will be jumping the cartridges back and forth from short to long.Nuts!

Is a hard jam in the comparator insert a better method of doing this. Or is there a better way to measure BTO consistently?

I use the Innovative Technologies tool for shoulder bump/headspace. Rotating the cartridge on the base yields a steady measurement. I do the same with the caliper setup and it’s not consistent


View attachment 1701044
are you using the correct seating stem? you may be seating off the point of the bullet
 
Referring to your first picture:
1) I do not JAM, I like to use as little pressure on the caliper thumbwheel as possible to get a steady reading.
(my hornady insert is aluminum, and I don't want to enlarge the hole by repeated pressure)
2) I have used attachments to the cartridge base such as you have. I found them to not be parallel to the caliper arms, so I stopped using them. Checkpoint.... with no cartridge case in place, caliper reading ZERO, can you see light between your base and the comparator head?
3) My Hornady comparator head is slotted off center, make sure you are measuring in a straight line parallel to the caliper body, if you are using a case base. or not using it.
 
Past the third number after decimal is a bit sketchy.
1.02345 (wanting 1.02300)
I use the 1.023 and if it's less than 5 or more than 5 rule on the fourth #. (The 3 is there how far past it am i ?)
The 5th number is also a gage in how close & how far i am going . I may try to get closer but that's a really small amount and it's not gonna be consistent because of brass base thickness difference. Find a middle ground i can live with.
 
I recently noticed that my hornady comparator and anvil when tightened become canted. The more you tighten the worse it gets. I messed with it for a very long time. It's impossible to prevent. Tighten them down and hold it closed while looking toward a light. You will see the light coming through on one side between the anvil and comparator. Going forward I wont use the anvil, but all my old measurements are off a couple thousandths without it. Maybe a different brand would be better, I dunno. Maybe it doesn't matter, but now it bothers me. Make sure you tighten the same way every time.
 
I would like to have a consistent measurement of my seating depth.
I use a Mitutoyo caliper with Hornady comparator tool and Sinclair insert.
I use this setup and can get just about any measurement I want by wiggling the base to ensure it is seated flat on the anvil.
There's a bit of technique with this setup in order to achieve consistent results. I use the same setup you have other than the insert which, for the Sinclair I believe is steel, mine is the Derraco Engineering which is anodized aluminum.

There are two points of contact; the cartridge base, and the bullet ogive. In theory, and practice for the most part, the base has no degrees of freedom from the gage base; it must be square to the base. The other end, the bullet ogive, has some angular freedom because it's a circle inside of a circle. That said, the more the ogive is tilted, the more it resembles an ellipse.

What I've found is that rotating the cartridge such that the base spins smoothly on the gage base, then bringing the insert gently onto the ogive until the cartridge rotates smoothly between the two points, provides consistent caliper readings.

It takes some practice.

Hope this helps.
 
View attachment 1701278This is the simplest and most accurate way to measure seating depth…all analog.


this ^^^
Why overcomplicate it with additional tools, attachments, devices, stacked errors etc.
------------
BTW, if you do not have a deft touch with your calipers thumbwheel
(wonders how anyone could use a 2 ounce trigger if so lol)
The caliper jaws can be closed with your fingers from outside the anvils also
The calipers are not a vise, they only need to close until a slight positive resistance is felt
You may also - Wiggle the comparator nut so the bullets ogive seats into the hole
As opposed to applying leverage on the thumbwheel to seat the bullet into the comparator
This only deflects the beam of the caliper showing inconsistent readings
 

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