Does seating depth truely matter?

[moe africa]

Good Day all
I recently performed a seating depth test on my 308 Win from 80 thou Jump to 150 thou
The reason for such large jumps are mag length constraints and a large freebore
The results are in the Hi Vis target
This was shot at 300m (327 yard) from shot 17 to 24 i did change my wind hold as the shots were getting difficult to spot
The total vertical was around 2.7 inches for 24 shots
I then loaded up 21 of the same charge and seating depth (CBTO = 2.205) and shot a group at 300m which measured around 4 inches , note the powder used here was a collection of the left over powder in the powder measure Yet the SD of both strings were 7.5 and velocity avg was within 1fps of each other
I don't know what do make of this data?
I've tried a few statistical analysis options
Such as levenes test , welches anova and a few post hoc tests (not a statistician)
I great deal of variation could very well be shooter error
Any insights would be appreciated

 

[6BRA]

Yes!

 

[Chaotik]

Yes!

^^^^^^

 

[jelenko]

Not sure what you're asking for.
Why didn't you keep track of group size vs seating depth?

 

[moe africa]

Not sure what you're asking for.
Why didn't you keep track of group size vs seating depth?

I did
In the red the group sizes for 2 consecutive seating depths are noted
Forgot to write down the individual depths and their sizes
Yet if 1 depth has more vertical than the entire test then perhaps the variation within the test is due to chance ?

 

[jelenko]

I think you want to look at group size for the various seating depths and choose the seating depth that has the smallest group. You can adjust for vertical with your sights.

 

[rkb21]

Yes a bunch

 

[TTE]

Bullet seating depth does matter.

Primer seating depth - (unless you are measuring your primers) ...... quite a bit less

 

[dryhumor]

I have a 308 that likes 150 grain bullets over 44 grains of Varget. The only variable I’ve found is the type of bullet used wants it’s own seating depth. I really don’t even vary the charge weight, I just vary the seating depth.

 

[Bill Norris]

Good Day all
I recently performed a seating depth test on my 308 Win from 80 thou Jump to 150 thou
The reason for such large jumps are mag length constraints and a large freebore
The results are in the Hi Vis target
This was shot at 300m (327 yard) from shot 17 to 24 i did change my wind hold as the shots were getting difficult to spot
The total vertical was around 2.7 inches for 24 shots
I then loaded up 21 of the same charge and seating depth (CBTO = 2.205) and shot a group at 300m which measured around 4 inches , note the powder used here was a collection of the left over powder in the powder measure Yet the SD of both strings were 7.5 and velocity avg was within 1fps of each other
I don't know what do make of this data?
I've tried a few statistical analysis options
Such as levenes test , welches anova and a few post hoc tests (not a statistician)
I great deal of variation could very well be shooter error
Any insights would be appreciated

Does seating depth truely matter?​

On a podcast called {Believe the Target) with Erik Cortina and Wayne Campbell who now has the second largest number of Hall Of Fame points (second to Tony Boyer only) Wayne positively says seating depth matters more than powder charge. He explains in detail why this is true.

I have to agree with Wayne that seating depth does matter a lot. I have no proof as to whether it matters more than powder charges but I would not question Wayne's ability to test and give his findings.

 

[Idaho-Lefty]

Did some Research on, good "seating depths" for, the 6 MM, 107 grain, SMK's for my 6 XC, on HERE, a few Years ago and Found that, a Light "JAM" on the Bullet, makes, a HUGE Difference over, "Jumping" them,.. HUGE !!!

 

[Timon]

Does seating depth truely matter?​

On a podcast called {Believe the Target) with Erik Cortina and Wayne Campbell who now has the second largest number of Hall Of Fame points (second to Tony Boyer only) Wayne positively says seating depth matters more than powder charge. He explains in detail why this is true.

I have to agree with Wayne that seating depth does matter a lot. I have no proof as to whether it matters more than powder charges but I would not question Wayne's ability to test and give his findings.

If you take nothing else from this interview, you should absolutely read Tony Boyer’s book.

 

[dellet]

This target with two different seating depths pretty much tells its own story. This happened while tuning a load, I was more concerned with trying to even out ES/SD so did not switch targets. More or less got this by accident.

First photo six rounds, second photo same point of aim another six rounds. The second six rounds were loaded .005” shorter. Note they are inside the spread of the first six.

 

[JFrank]

Here’s a 300 yard seating depth test from a few years ago that I alway felt told a pretty good story of how the group shape changed as the depth changed.

 

[G Liles]

I do mine in .003 increments.

 

[dryhumor]

I was gifted a box of 150 grain hunting bullets a couple months ago. Ten rounds, two seating depths, 90 bullets left. Not a lot of difference between seating depths, but enough to show up on target.

 

[Tangent]

I have a factory Tikka and had the same issue as the OP. I just went for max mag length, in my case 2.90", still a long way off the lands. Using Lapua 155gr Scenar-L and 44.0 of N140 the groups were good enough that shooter skill and wind reading were much bigger factors.

I have a 260Rem that I have a powder load in happy with, and I'm close enough to the lands 0.010" at mag length that I'm going to try a seating depth test. Hopefully that might tighten it up a bit more, but it's already looking pretty good.

 

[wright brothers]

Factory rifle
max mag length is
a long ways from the lands.

Can anyone answer WHY a rifle manufacturer does this?
Or what am I missing as advantage for this?

 

[Sandstorm]

Moe ...listen to the fellows and put out a horizontal target with some small X hairs and shoot some
3 shot groups with different seating staring with a .01 or .020 jump and work your way out in .003
increments... out as far as you feel like...youl find something for sure.
This way you can look at the vertical as well on a horizontal plane ( I shoot 7 -3 shot groups and done )
It makes a big difference with some bullets and smaller difference with some others but its there for sure.
enjoy the process Sir.

( Like the example by jfrank on post #14 )

 

[SeabeeKen]

With length restricted by mag length, the answer is self evident. Load longer and shoot single shot and you will surely find your answer