Seating Depth

[RUFFIAN R - NY]

maybe yes and maybe no: you tell us !!! Besides all guns are not created equal !!!! That goes for brass-bullets-lots of powder- primers- seating PSI -

 

[Mikecr]

Mikecr … I've always used the OCW method and have been looking into the satterlee ladder… I think I'll try this. I usually load to Mag length but I'm about to work up a load for my #1B so I was already thinking about playing with the seating depth.

I haven't suggested anything for load development. You can do OCW and any other tuning method.

Coarse seating testing is not load tuning.
Primer swapping is not load tuning.
Fire forming of brass, and rest bag filling are not tuning.
These are prerequisites to tuning.

Tuning is powder, and barrel timing, which like everything else, are separate and completely different.
You can find an optimum powder charge, which is most forgiving burn. Grouping may or may not be good with that.
You can find cutting edge grouping, with or without an OCW load.
You could ignore one aspect or the other, or combine them with a barrel tuner.
But no matter what, wrong seating or wrong primer* to begin, will not allow the best in final result.

We have the adage: there is more than one way to skin a cat.
But if we actually understood cat skinning, we would know the best way to skin a cat, and we could describe it logically.
So when I see everyone skinning cats differently, and they all think they're right, then I'm sure it's not widely understood.
When people don't or can't logically describe WHY they skin cats a certain way, then I KNOW they don't understand it.
No reason to believe any of them, no matter how much experience they have at doing it wrong.

I watched for 2 decades many top competitors, and pretty much all their chronies and gun rags broadly declare that VLDs had to be in-the-lands (ITL) to shoot. They knew it, and some had trophies. When challenged on it, they insisted that they had tested and proven it to themselves. Thing is; they were wrong,, they never actually tested it,, there never was a logical basis for the notion.

I certainly tried and failed to convince people of these things, but finally, when Berger put it out, they listened..
As far as I know Berger never described WHY bullets prefer a random but specific seating for best results.
That tells me they don't understand it (which is fine).
But people finally tried it, and found that VLDs do not have to be ITL to shoot.
Was there ever a reason for folks to believe me 20yrs earlier?
No more than I have reason to trust the last 100yrs of whatever they're doing..

*There is no wrong primer. Instead there are primers which favor, or hate, YOUR striking.
You could pick any primer, and optimize striking for it, but swapping is an easy/coarse action.

 

[Equalizer]

So how do you know the difference in primer "striking"? I have to be honest I usually just use what primers I have the most of and the one time I tried a primer swap on a proven load it opened up my groups…

 

[Mikecr]

So how do you know the difference in primer "striking"?

You don't. There are a lot of things affecting striking and zero standards for it.
We have failed to define optimum striking for primers in general, much less different primers.
This would be a term similar to N/Sec^2/Std-area, and we would need a method of measure, and an easy way to calibrate it.
Primer space and crush would also be in the standard.

So what we're left with is an unaddressed abstract (a mess).
If you change to a titanium firing pin, let a spring weaken, or change a trigger, you have no idea what that will do to your grouping.
You might have to change primers, or go back to load development.
Or, you could re-optimize your striking.

Once I was forced to address an intermittent striking issue with an otherwise consistent 3/8moa at 500 hunting gun.
All primers fired, but here & there I would get an errant shot fully 3/4moa off my mark.
This screwed me over bad, as it was not an easy problem to figure out.
It turned out that the firing pin was slipping under it's set-screw.
Worse, there were no markings on the pin to see where it was originally set.
So I had to fire a group, adjust the pin, fire another group, repeat around 10 times, and then validate.

What I found was pretty much just like full seating testing. Grouping opened, closed, reopened.
And like seating, there was magic in this. It turned out that optimum striking gained me 1/8moa over my prior best.
In my lifetime, I would never have seen that hidden 1/8moa, without this problem & solution (curse to blessing).
I ended up making and installing a bushing in the bolt, so that this pin setting could never change again.

My next custom action, or maybe even one I already hold, will have adjustable pin setting from the back of the bolt shroud.
With that I'll test every different primer to see if optimum changes. I'm confident it will given the abstract primer choices people have ended up with. Validation is tricky in that I will need to powder develop at optimum, and off optimum, to isolate the real affect here.
If I'm really on to potential, then I could solve striking force/speed/area measurement to define what's what.
Or, die of old age before getting there... There is that...

 

[Lonewolf74]

Mikecr; I'm interested now in hearing your method of primer testing. Is it as simple as trying different primer's once you have found optimum seating to see what groups best? Then on to tuning with powder? Something tells me it's not that straight forward.

Either way I'm fascinated and believe I may try this with a new custom that I've done no development for and an older custom with established load to see if I end up in the same place.

 

[Mikecr]

Normally, while between powder nodes, I just swap 5 or 6 primers, and look for lowest SD on my chronograph.
It's not going to be great there, but I can see a clear winner, and it's not going to get worse when I'm in a powder node.
Again, this is not tuning, but prerequisite to tuning.

 

[smokey3]

Over my 50 years of handloading… seating depth was the single adjustment to dial in extreme accuracy.
Benchresters of the day(80s90s) claimed this…I ran my own tests to confirm.
From bullet jam to .020 off the lands showed clearly which seating depth a particular bullet prefered.

In my youth I followed gun writers advice trying every which powder and bullet and technique….burning powder and barrels…wasted energy…

The Nosler loading manuals always gave a "best load tested" indication and a most accurate powder tested…

In the calibers I loaded Nosler was never wrong and using the correct seating depth gave me phenomenal accuracy with the minimum amount of component expended….and their recommendations worked over multiple barrels and guns in a given caliber.

my 8 cents worth

^^^
I have found the same results and have posted that on this site more than once and one of my Nosler reloading books is from the early eighties, volume #3. They have saved me lots of components over the years and that is more important now than ever. I have always cherished accuracy over sometimes higher velocities.