Seating depth - does it even matter?

[Harvey_NW]

With all the data from Hornady flying around and all the testing I've done, I find they align and I'm convinced seating depth doesn't matter at all, or if there is a distinguishable difference in my hunting rifle I don't want to waste the components to prove or find it. Curious if anyone has proof or documentation of decent sample sizes where a certain seating depth shot noticeably better than another? Not 5 shot groups either, I'm talking minimum 10 both samples.

 

[nhyrum]

https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf

An article written by Bryan litz. He's the chief ballistician at Berger and applied ballistics. He regularly shoots and wins the king of two miles. He knows a thing or two about bullets and bullet design

I have seen a difference personally in groupings and velocity spreads by changing just the seating depth. It does matter, but it's only a small piece of the puzzle

Sent from my SM-S918U using Tapatalk

 

[Harvey_NW]

https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf

An article written by Bryan litz. He's the chief ballistician at Berger and applied ballistics. He regularly shoots and wins the king of two miles. He knows a thing or two about bullets and bullet design

I'm very familiar with Litz and his findings, but that article is more of an overview of the effects of changing CBTO. It was also written in 2013, and what I find interesting is his view on sample size and the effects of seating depth now. In a recent podcast with Cortina he starts to align with the Hornady guys talking about the nature of dispersion and random distribution, and how much it takes to actually distinguish a difference. It's a long one but it's packed full of good info, I listened to it a few months ago. But I skipped to about the 15 min mark just to confirm it was the one I was looking for and landed on that coming from him with the contract work he's been doing.

I have seen a difference personally in groupings and velocity spreads by changing just the seating depth. It does matter, but it's only a small piece of the puzzle

Sent from my SM-S918U using Tapatalk

I have too, doing small sample testing. That's kind of the crux of my question, does anyone have larger sample sizes to prove their findings? Even 10 shots has a ton of variability, but it starts to paint a picture. All of these ballisticians are aligning with the fact that nodes don't exist, and it takes an immense amount of work and components to actually distinguish a difference between changes to a seating depth, or powder charge.

 

[Pharmseller]

Observe the difference in groups. The only change is seating depth.








My process is to start by just kissing the lands, then work backwards. It’s the Berger method. Works well for me.





P

 

[bmart2622]

Your velocity changed too

 

[Ryan Avery]

It matters, and it's really easy to see if you do load dev from 600 to 800 yards. But then again some rifles just don't seem to care either way.

 

[Lawnboi]

I think the type of bullet might make a difference. I tend to use bullets that are supposed to be forgiving on seating depth.

I havnt really seen seating depth make that much of a difference. Where I have is on compressed charges that got erratic when I started to crunch too much. And vld style bullets.

 

[bmart2622]

Observe the difference in groups. The only change is seating depth.

View attachment 557613

View attachment 557614

View attachment 557615


My process is to start by just kissing the lands, then work backwards. It’s the Berger method. Works well for me.





P

So the smallest group was the first one you shot?

 

[Pharmseller]

So the smallest group was the first one you shot?

No, the last. I start with the shortest cartridges first, because if I find accuracy short I can reseat the longer ones.

I haven’t figured out how to make the short ones longer.




P

 

[bmart2622]

Oh ok, I thought you said you started by kissing the lands and working backwards, wasnt sure if I was seeing the numbers wrong

 

[Pharmseller]

Oh ok, I thought you said you started by kissing the lands and working backwards, wasnt sure if I was seeing the numbers wrong

That‘s the process for creating the cartridges. I load 5 of each seating depth. On range day I start with the shortest cartridges first.

Read this:

Getting the Best Precision and Accuracy from VLD bullets in Your Rifle

VLD bullets are designed with a secant ogive. This ogive shape allows bullets to be more efficient in flight (retain more velocity = less drop and wind deflection). While this result is desirable for many rifle shooters the secant ogive on the VLD bullets produces another result in many rifle.

bergerbullets.com

I have found this process is suitable for bullets other than Berger as well.





P

 

[9.1]

I haven’t figured out how to make the short ones longer.

 

[bmart2622]

I load them for max mag length since I know Im not going to single feed. With Berger hybrids that's put me around .40 off the lands which most rifles have seemed to like

 

[N2TRKYS]

Haven’t had it to change accuracy or change velocity any whatsoever.

 

[bmart2622]

Never had it not change velocity

 

[Rob5589]

I've found it to matter with some bullets, not at all with others. I shot a bunch of SMK's which were depth insensitive; the Amax (eldm predecessor) were depth sensitive. ELDX don't seem to be depth sensitive, TTSX don't care where you load them.

 

[Harvey_NW]

Observe the difference in groups. The only change is seating depth.

Very interesting, what cal? There is some theory about older chamber design vs newer playing a role in this, but those are notably different. I'm still curious what the outcome would be if both were taken to a significant sample size.

 

[ID_Matt]

Observe the difference in groups. The only change is seating depth.

View attachment 557613

View attachment 557614

View attachment 557615


My process is to start by just kissing the lands, then work backwards. It’s the Berger method. Works well for me.





P

Going from a 3" group to a 0.62" group is wild. Wonder if that has more to do with them being a VLD vs a hybrid type

 

[JFK]

I believe that it only really matters when you are getting very close to the lands or jamming the bullet. Doing so creates a pretty volatile situation where small changes can positively or negatively impact pressure and accuracy. I typically start load development at .050 or
more off the lands and have never seen a discernible difference in making small changes in seating depth.

 

[ID_Matt]

I am not sure if I have gotten lazy with my load development, or just don't think it matters too much. I don't pay near as much attention to seating depth as I used to. I will usually test 5 shot groups somewhere up close - like 30 thou off and something big like 120 thou off. Whichever one shoots better, I will do a 10 round group to confirm. I can't say I have ever done large sample testing though, and I do agree with some of the hornady philosophy that it would take very large samples to really be able to distinguish.