Question

[rplaw]

In this case, then I'd true the base until it's dead flat and perpendicular to the case wall.

Then I'd make a jig to stand the loaded round perfectly vertical and measure with a dial indicator for overall length. The jig could be nothing more than a donut with a hole sized for the case at least half as tall as the case. All it has to do is hold the case perfectly vertical without letting the case move while you measure length with the indicator.

Adjust the seating die on the press until you get the overall length under the indicator that you want.

[Dirtlaw]

In this case, then I'd true the base until it's dead flat and perpendicular to the case wall.

Then I'd make a jig to stand the loaded round perfectly vertical and measure with a dial indicator for overall length. The jig could be nothing more than a donut with a hole sized for the case at least half as tall as the case. All it has to do is hold the case perfectly vertical without letting the case move while you measure length with the indicator.

Adjust the seating die on the press until you get the overall length under the indicator that you want.

But for truing the face, that's exactly what I've done.



Instead of truing the base I've "trued" the indicator by using a pancake point instead of the standard point so the measurement is not affected by the particular point where it is made -- it just measures from the highest spot. Also I'm "polishing" the base with 1500 grit to see if there are any high spots on the brass. Little material is removed. Actually it makes the headstamp more distinct.


The above is essentially an experiment to see if truing the base is an issue. It could be that imperfections in the base cause the variation. Polishing should eliminate that.


When I'm done I should be able to adjust die parameters quite accurately.

[Dirtlaw]

But for truing the face, that's exactly what I've done.



Instead of truing the base I've "trued" the indicator by using a pancake point instead of the standard point so the measurement is not affected by the particular point where it is made -- it just measures from the highest spot. Also I'm "polishing" the base with 1500 grit to see if there are any high spots on the brass. Little material is removed. Actually it makes the headstamp more distinct.


The above is essentially an experiment to see if truing the base is an issue. It could be that imperfections in the base cause the variation. Polishing should eliminate that.


When I'm done I should be able to adjust die parameters quite accurately.

Thus far I'm pleased with the progress I've made. That's my reward.

[Dirtlaw]

update

I'm now using a "disk" or "button" point on my dial indicator to avoid basing the reading on a specific spot. At first blush the variance seems to be settling down. This is an area I want to further explore. I'm starting with an indicator that reads in thousandths, to be followed by one that reads in tenths and ending with one that reads in two hundredths [admittedly overkill, but then again I'm having fun playing with my toys .]

[sigstroker]

In almost 3/4 of a century I've only found four instances of perfection.

Hot twin sisters with great racks?

[Dirtlaw]

Hot twin sisters with great racks?

God ranks first of course, and my wife is also in the race to be named. Exceptional or amazing can often be found ... on the other hand, perfection is exceedingly rare.

[divingin]

I'm now using a "disk" or "button" point on my dial indicator to avoid basing the reading on a specific spot.

I assume you're talking about OAL of the cartridge?

While you have your measurement tool set up, try measuring a couple of dozen bullets for OAL, followed by getting ogive to tip for each. I suspect you'll get as much discrepancy there as you do measuring cartridge OAL.

Just for fun, take a look at meplat trimming and bullet pointing tools.

[Dirtlaw]

I assume you're talking about OAL of the cartridge?

While you have your measurement tool set up, try measuring a couple of dozen bullets for OAL, followed by getting ogive to tip for each. I suspect you'll get as much discrepancy there as you do measuring cartridge OAL.

Just for fun, take a look at meplat trimming and bullet pointing tools.

THANK YOU DIVINGIN!!!! I love it when someone stretches my knowledge. My measurements are improving and that is hugely gratifying. I am discovering little errors I have made. But what is thrilling is everything gets better. The positive (I guess) is that I have to rid myself of all the rounds that are less than perfect. And that means the opportunity to hone my shooting skills! The bad guys appear to be letting me off the battlefield ... for a time at least ... so I have been having a wonderful time playing with the toys I have acquired while acquiring a few more. The tools I always wanted growing up. It's a happy time for me.

[Dirtlaw]

The sad part is that my very high precision dial indicator passed away. I don't know if it can be saved.

[Dirtlaw]

At the moment I'm working on improving the quality of my gauge block accessories. So if anyone out there has a "deal" please let me know.

[LynnJr]

Dirtlaw
As Diving in posted bullet variation can be huge.
In a typical tool it makes contact around the 0.218 - 0.219 diameter on the ogive of the bullet. If you measure the base of the bullet to this point using a comparator you can see 0.023 inches in a box of 100 bullets.
The reason for the variation is most of the bigger companies use multiple dies when making bullets and they all get lumped together.
Sorting bullets is a common practice ongst match shooters.

[AGGRO]

I too think of these things when it's raining out and I'm bored, really bored.

[ar15barrels]

The base of the case is the reference point for some important measurements.
It is stamped but not machined.
What issues would arise if you very slightly machined the base so that it was perfectly flat and perpendicular to the walls of the case?

Headspace gets increased by the amount of material removed.
The whole case is semi-fluid when at it's peak pressure so having the case head square at one time won't guarantee that it STAYS square after it's been fired as many breech faces are not even perfectly square to begin with.

[ar15barrels]

The sad part is that my very high precision dial indicator passed away. I don't know if it can be saved.

https://www.ebay.com/itm/284371621807

[Epaphroditus]

New unfired cases get fire formed with lube so the entire case gets reformed. Particularly for belted magnums.