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How To Get Consistent Seating Depth Every Time from an empirical source.

FEENIX

FEENIX

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Dec 20, 2008
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Now that I have your attention 🤣 , "no," this is not necessarily empirical as to how or why reloaders test various seating depths. I also understand a lot of people do not care about Gavin. However, I think he did an excellent job addressing the elephant in the room. Take it for what it is worth. As with everything else, YMMV.

 
My take (without watching the video). For the perfect seat, you need perfectly consistent neck tension, perfectly annealed necks, and perfectly shaped bullets, a good consistent press...and a high quality digital caliper.

I can seat to within .0005" CBTO (I never measure COAL due to meplat differences, even with tipped bullets, Bergers, etc.) 98% of the time with once fired, freshly annealed, with just a bit of carbon left in the neck brass and either Berger or Sierra bullets. Some other bullets are far less consistent.
 
lancetkenyon said:
My take (without watching the video). For the perfect seat, you need perfectly consistent neck tension, perfectly annealed necks, and perfectly shaped bullets, a good consistent press...and a high quality digital caliper.

I can seat to within .0005" CBTO (I never measure COAL due to meplat differences, even with tipped bullets, Bergers, etc.) 98% of the time with once fired, freshly annealed, with just a bit of carbon left in the neck brass and either Berger or Sierra bullets. Some other bullets are far less consistent.
Click to expand...
SAMEZIES!!!

And i will take it a step further and add... a constant steady downward stroke of the press handle to a soft stop every time all the time

CONCISTANCY is key!
 
Elk Hunter 338 said:
There really is only one brand to buy for ultimate accuracy ...... MITUTOYO!!!
Click to expand...
Interesting…. From Mitutoyo's website:

"Caliper Accuracy
The measurement accuracy of the caliper, sometimes termed instrumental error, may be expressed in steps. The first step for the 0-200 mm (0-8 inch) range shows a measurement uncertainty of ±0,02 mm (±.000 8 inch) over this range (when set to zero with the jaws closed) which increases by around ±0,01 mm (±.000 4 inch) for each additional 200 mm in range thereafter. This trend continues all the way up to 1000 mm."


Meaning, the instrumental error is 60% greater than your expressed "concistancy" of .0005".

Even with the induced margin of error, you're loading to a very consistent length, it's just not as consistent as you presume.
 
WA Coyote said:
Interesting…. From Mitutoyo's website:

"Caliper Accuracy
The measurement accuracy of the caliper, sometimes termed instrumental error, may be expressed in steps. The first step for the 0-200 mm (0-8 inch) range shows a measurement uncertainty of ±0,02 mm (±.000 8 inch) over this range (when set to zero with the jaws closed) which increases by around ±0,01 mm (±.000 4 inch) for each additional 200 mm in range thereafter. This trend continues all the way up to 1000 mm."


Meaning, the instrumental error is 60% greater than your expressed "concistancy" of .0005".

Even with the induced margin of error, you're loading to a very consistent length, it's just not as consistent as you presume.
Click to expand...
"Repeatability .0005"/.001mm".
 
.0008 instrumental error, is 60% larger than your presumed level of accuracy of .0005. So, you are correct, that would indicate +/- 60% or 120% total margin of error.

Like I said, that's meaningless, but not as precise as stated or presumed, as there's no way to accurately measure to that level of precision with a simple handheld too.
 
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WA Coyote said:
.0008 instrumental error, is 60% larger than your presumed level of accuracy of .0005. So, you are correct, that would indicate +/- 60% or 120% total margin of error.

Like I said, that's meaningless, but not as precise as stated or presumed, as there's no way to accurately measure to that level of precision with a simple handheld too.
Click to expand...
Most calipers, if not all, have a tolerance of +/- .xxx and micrometers +/- .xxxx. However, calipers might indicate 4 decimal points, i,e., .0005" increments. Who cares if it indicates .0010" or .0005." If you want to argue about margin of error or level of accuracy, argue with the guy on the video below.



I am pretty sure @Elk Hunter 338 as a gun builder knows.
 
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