Seating depth advice

Veteran

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By the way, I meant to add if you were using the Berger VLD's you would have to use an Ogive to lands measurement. Coal would be totally wrong using those or any Secant or really long nosed design of bullet. You can have the tip of the secant bullets up into and past the lands and not even touching the lands, so the real measurement of jump that matters then is the ogive to lands measurement where the bullet will actually first contact the lands
 

Mikecr

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Seating is your coarse adjustment, powder is a fine adjustment.
You're doing this testing backwards in that you're adjusting coarse with concern for fine.

If your sure you're beginning in a powder node, then get away from that node and do coarse seating testing purely for tightest coarse grouping. Your best grouping with that might be 2moa, doesn't matter, you're finding best seating.
Then with best coarse seating, go back to your powder testing, but watch grouping.
Then finish with fine seating adjustments within it's window. Tweaking for tightest group shaping.

Your ES/SD may be higher or lower, but accuracy will trump it.
There are other ways to lower ES.

In reality, seating action is not tuning at all. And neither is primer striking adjustments.
They are prerequisites to good tuning.
Tuning consists of powder, vibration, and sys recoil.

The reason you can have fantastic accuracy at distance even with higher ES, is because the vibrational node is flattening out, or compensating, for powder node character. So don't get all hung up with a chronograph until at least finding your most powerful of ballistic attributes (accuracy).
 
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JohnyRingo

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I loaded up 5 rounds at 3.605" and 5 rounds at 3.610". I did adjust the powder charge to see how 67.3 grains will perform.
 

L.Sherm

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In reality, seating action is not tuning at all
Then why do all the 1,000 BR shooters I know do seating depth ladder tests right before every match. Ive watched matches were they do final seating right before they sit down to shot.
Short range not so much.
 

Mikecr

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In general, unless seated land relationship is relied on to hold a high starting pressure(i.e. in the lands), then seating does not have to be readjusted once found -with that bullet, -for the accurate life of the barrel.
The BR shooters who do adjust seating(commonly) are the point blank shooters. This, because they're shooting underbores that absolutely rely on certain starting pressures(6PPC, 30BR, etc). They also need tightest cutting edge up to the minute group shaping.
I suppose seating could be tweaked(slightly) at 1kyd for tightest/up to the minute group shaping also.
But we're talking about potentials different from full seating testing.

CBTO is a coarse adjustment to results that is not tuning for all but maybe 1 in 10,000 shooters(non PB BR).
It is little different than primer/striking adjustments. Did you know that you can open-close-open grouping with firing pin fall adjustments? You can, and it's not tuning. It's merely coming in & out of optimum for the chosen primer and crush.
With seating, it's similar in that you're coming in & out of optimum bullet-barrel interfacing.

A side affect of large CBTO adjustments is minor changes of load density and neck tension. This can affect the character of POWDER TUNE. It can collapse an edgy powder tune, and that's why full seating testing should be clear of any powder tune.
You want to see results of full seating testing in itself, and THEN move on to actual tuning.
You want to get your best primer/striking, and rest/bag adjustments before moving on to tuning as well.
 

L.Sherm

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Well I know they change seating depth to conditions from match to match if thats not " tuning" i don't know what tuning means then.
 

Mikecr

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Seating depth to conditions?
Does that make any sense?

I think you mean that some of them chase lands.
A poor choice with that..
 

J-B welder

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Well I know they change seating depth to conditions from match to match if thats not " tuning" i don't know what tuning means then.
I was thinking the same thing. Different people apparently mean different things when they refer to "tuning."
 

QuietTexan

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Which CBTO tool do you recommend using? I have just been using the OAL.
Hornady makes a cost-effective set that's perfectly functional for a lot of people (I use this set):

And Short Action Custom makes a much more expensive, but more precisely cut set for people trying to minimize every variation that they can:
 
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