Seating depth in a .300 Win Mag

[bowhunter123456789]

Question about seating depth? Lets take the 210 gr Berger VLD for a bullet. Would the seating depth change with charge weight or does the seating depth stay consistent regardless of charge . If so ,seating depth tunes the bullet to the barrel and charge weight tunes barrel harmonics.Would I be right to assume this? Thanks Mark

 

[Mikecr]

There are 2 things you tune with; powder, and neck tension.
Seating depth, like primers, doesn't 'tune' anything.
Best seated position is simply prerequisite to best results -regardless of tune.

On tuning, there is incremental load development (for precision) or optimum charge weight (for load forgiveness). These are different animals.
Optimum barrel time is not tuning, but clearing of a detrimental vibration condition.

There are underbore cartridges that rely on high starting pressures, and both seating and tension can provide it. For this you sacrifice tension from tuning, to provide a needed prerequisite condition. This doesn't apply well to hunting size cartridges, so dismiss those doing this when they suggest that you need to FL size necks, or jam bullets into lands.

Once you've set best seating for a bullet, off the lands, you don't have to change seating again for that bullet, for the rest of that barrel's accurate life (even while changing powders/lots).

 

[ShtrRdy]

Mikecr - regarding neck tension - what have you found to be the best practice for preparing the inside neck? Leave all firing residue? Run a brush on the inside neck to remove some firing residue? Squeaky clean? Do you like to use any sort of lube inside the neck before seating the bullet?

 

[ShtrRdy]

Question about seating depth? Lets take the 210 gr Berger VLD for a bullet. Would the seating depth change with charge weight or does the seating depth stay consistent regardless of charge . If so ,seating depth tunes the bullet to the barrel and charge weight tunes barrel harmonics.Would I be right to assume this? Thanks Mark

I don't know the true answer to your question but I can pass along what I found. I have two 300 Win Mags. One for hunting and one for long range shooting. I use the Berger 210 gr VLD in the long range rifle. I found that I got the best accuracy when I seated the bullet touching the lands. Ber has a paper on their site which describes a procedure to determine seating depth for the VLD. It didn't work for me but others claim to have had good results.

It seems like changing seating depth would change the volume in the case, so in order to end up with the same velocity you would have to change powder charge weight.

Once you find a "good" seating depth for a particular bullet you can change powder charge weight and leave the seating depth the same.

Maybe one of those sentences will help.

-- Todd

 

[Mikecr]

Mikecr - regarding neck tension - what have you found to be the best practice for preparing the inside neck?

Seating friction and neck tension are completely different things.
There is no direct correlation between them.
However:
The carbon layer shooting provides is a perfect neck lube. Very consistent.
I run a nylon brush through necks once before vibratory cleaning. That's it.
With this, and sizing to 1thou interference, and consistent brass hardness, and clean dry bullets, I can use seating forces to comparatively indicate neck tension variances.

I adjust neck sizing LENGTH to match seating force/~tension across my ammo.
I can measure this -before seating actual bullets, with an instrumented mandrel die, and bushing neck sizing.

 

[bowhunter123456789]

So seating depth is the distance to the lands let's say ,what ever the bullet prefers= better accuracy. So the amount of bullet within the case is not what seating depth is all about. But a longer seating depth will yield more case capacity.
So this brings up another question, if the powder charge produces a compressed load , should you try a faster powder?

 

[Mikecr]

Changing seating depths with testing also affects neck tension(potentially) and load density.
These are relatively fine to the coarse affects of seating changes, but enough to take a load that's in tune, to out of tune(which becomes a 2nd coarse factor).

For Berger method testing they recommend you back way off from your max load.
Safety aside, it's also important for identifying best seating alone. You need to get away from any powder node, which is typically near full case (with the right powder).
Ideally, you would test seating with a load that is nearly worst.

Now you might be thinking 'how can I find best seating while spraying bullets out there at ~1moa(or worse)'?
You can because seating is very coarse to results. Seating alone can open/close grouping by ~3/4moa. This of course depends on many things, but seating alone is always bigger than powder alone.
And with anything calibrated you adjust coarse first, then fine, & finest.
Coarse is seating and primers (prerequisites), fine is powder(right to the kernel), tension, and group shaping with final seating tweaking(within it's coarse window).

You can do full seating testing, and primer swapping, while fire forming of brass.
Then, with fully fire formed & stable cases, test powder loads. If any parameter were pulled out your butt here it should not be seating, it should be beginning neck tension. A good rule IMO is 1thou interference at 1/2 neck length.
After dialing in a powder/tension load, tweak seating in it's coarse window to shape your grouping without collapsing your node so far. This would likely be within a 10thou window. The window for one of my guns is 8thou.

I don't have a procedure for it yet, but primer striking is another prerequisite. You can open and close grouping with striking adjustment for a chosen primer. I don't know the how or why, it makes no sense to me, but I tested this once and saw results similar to seating testing. A solid 3/8moa gun opened to ~3/4moa, back thru my 3/8, to 1/4moa, and then opening again, with 10thou adjustments in released firing pin protrusion from bolt face.
I never would have found that 1/4moa(solid) doing what everyone on this planet is doing...

 

[ronstone09]

Question about seating depth? Lets take the 210 gr Berger VLD for a bullet. Would the seating depth change with charge weight or does the seating depth stay consistent regardless of charge . If so ,seating depth tunes the bullet to the barrel and charge weight tunes barrel harmonics.Would I be right to assume this? Thanks Mark

Seating depth is on of final steps in developing a load ! 1st pick a powder,then ladder test for ideal load, then experiment with seating depth until you find one your rifle likes !

 

[bob4]

Question about seating depth? Lets take the 210 gr Berger VLD for a bullet. Would the seating depth change with charge weight or does the seating depth stay consistent regardless of charge .

I believe that the seating depth for that bullet in that rifle stays the same. Different bullet different rifle all bets are off.

 

[bowhunter123456789]

No doubt , each gun would be different

 

[Mikecr]

Seating depth is on of final steps in developing a load ! 1st pick a powder,then ladder test for ideal load, then experiment with seating depth until you find one your rifle likes !

Hogwash..
Once you've found a powder node using some seating you pulled out of your butt, and alter seating much at all (way less than full seating testing) from that point, your powder node will collapse. So you'll tweak seating very little, finding best only within a few thou of your initial, as everything else will seam worse.
You'll pat yourself on the back for finding(knowing) best seating while very likely never determining actual best seating. This, like most reloaders, as I know you got this brilliant plan from them.

If you followed internet forums and magazines for the past 30yrs, you would have noticed for at least 15 of them, everyone declared and just knew that VLDs had to be into the lands to shoot. It's still the basis today of so much worrying about being able to reach lands. But, none of it was ever true.
Some of us countered with random findings that VLDs shot fine off the lands, often at surprising distances from lands. The 'experts' continued to claim otherwise, and it eventually became pretty clear that their method in coming to this conclusion is as you just touted.
They were never REALLY doing full seating testing, and even with some trying it, they did it wrong. Well recently Berger went ahead and tested and provided a method to reproduce better results(their better results). Then with this kind of credibility, people tried it and found that for the last ~15yrs the experts, and all of their followers, were dead wrong. That VLDs actually rarely shoot best while ITL.

It has recently been discovered that intelligence drops with numbers. That in any group of 10, 100, or 1,000 collaborating on problems, their collective solutions are less likely correct than any one person in that group 'could' resolve(even the dumbest).
Basically, this explained 'mob mentalities', as demonstrating nearly zero intelligence, and ultimately why a true democracy will never succeed.
But it didn't really take grants and careful studies to conclude this. Our founding fathers knew it and built a republic -instead of a democracy.
Their only real mistake was a free press.. That was too optimistic,, too mob forming..

What I'm saying here is don't be afraid to step away from our mob. To consider the possibilities, as very possible, that the mob is wrong.

 

[338 dude]

Mikecr - regarding neck tension - what have you found to be the best practice for preparing the inside neck? Leave all firing residue? Run a brush on the inside neck to remove some firing residue? Squeaky clean? Do you like to use any sort of lube inside the neck before seating the bullet?

Leave carbon in the neck lightly brush that is all

 

[bowhunter123456789]

When you are testing for best seating depth and best powder charge , is it recommended to shoot at 100yds ? My rifles are zeroed at 200yds , any advantage too testing at 100 yds vs 200yds?

 

[bowhunter123456789]

Found my answer in another thread ,Thanks