Seating depth - does it even matter?

[huntnful]

Thanks. I think it's about the limit of my ability to shoot consistently with an 8lb rifle prone off a bipod & rear bag.

I routinely achieve this level of precision following the approach of:
1. Seat 0.050 off
2. Powder charge estimated to get the velocity level I want
3. Done

with a well-built rifle & good barrel. And good components.

Same here. But I normally do .010-.020 off

 

[zrodwyo]

Last week, I shot a 20-round group with my go-to 6.5 SAUM load as a control. I’ve done this many times, so I have a solid understanding of how the rifle groups. Next, I shot a 30-round group with seating depths ranging 0.100 inches from the longest to the shortest. Some of the rounds had been sitting on the shelf for two years, while others were loaded that day. The group with varying seating depths fell within the normal distribution, and the muzzle velocity standard deviation (SD) was also within the normal range.

My takeaway from this test is that I’m not willing to burn through components to determine if seating depth significantly impacts group size. The amount of rounds that it would take to do load development would burn out a barrel.

I’m sticking with my belief that a barrel either shoots well or it doesn’t. If a barrel can’t produce good groups with a near-max load using the bullets and powder I stock piled, it’s going in the trash.

 

[Harvey_NW]

Last week, I shot a 20-round group with my go-to 6.5 SAUM load as a control. I’ve done this many times, so I have a solid understanding of how the rifle groups. Next, I shot a 30-round group with seating depths ranging 0.100 inches from the longest to the shortest. Some of the rounds had been sitting on the shelf for two years, while others were loaded that day. The group with varying seating depths fell within the normal distribution, and the muzzle velocity standard deviation (SD) was also within the normal range.

My takeaway from this test is that I’m not willing to burn through components to determine if seating depth significantly impacts group size. The amount of rounds that it would take to do load development would burn out a barrel.

I’m sticking with my belief that a barrel either shoots well or it doesn’t. If a barrel can’t produce good groups with a near-max load using the bullets and powder I stock piled, it’s going in the trash.

Agreed. I've done a similar test with neck tension from stuff that was loaded for a long time and I ended up having issues and pulled bullets to diagnose (tight on close from primers not fully seated), when loading back up bullets seated with very little resistance and I even added a new lot of bullets into the mix. All fell within the expected cone.

 

[TheWhitetailNut]

You guys dont know what you are talking about. You are regurgitating fuddlore.

Have any of you performed modal analysis? What is your experience with structural dynamics? How are you testing the effects of harmonics on your accuracy? Do you have an FEM model that proves your claims? Can you provide your test results for analysis?

You are convoluting a simple process. you dont know what you are talking bout. Any challenges to the dogma are often met with aggression by "zealots" like you. Present some data and evidence and I will happily change my mind.

No. none of that. Probably the best shooter of our time said it. I tried it. It worked.

NO PFM required.

 

[Packmansion]

Thanks. I think it's about the limit of my ability to shoot consistently with an 8lb rifle prone off a bipod & rear bag.

I routinely achieve this level of precision following the approach of:
1. Seat 0.050 off
2. Powder charge estimated to get the velocity level I want
3. Done

with a well-built rifle & good barrel. And good components.

I follow the exact same formula. Works like a charm. I have yet to have a rifle that doesnt group well with this approach. Instead of fiddling with depth and charge I collect data on my SD and use that to determine my wez.

 

[greyghostnw]

Seating depth. Does it matter. That is the title. After skimming through the responses and thinking’s about why one would respond positive or negative to it i determined at least for i my response should be considerate of the intention or phase of load development.

For the initial point of development I determine if im going to single feed or feed from mag for initial starting depth. If mag length dosnt matter i choose .020 off touch as a gaurd rail with the bullets i use it is a great starter in my past barrels and component combos…but could be less or more. Any closer i know i dont want for hunting to allow for foreign matter and function though. I could start anywhere it dosnt matter to some extent .. I can make a load from really any starting depth from powder charge, seating depth, diameter interference fit with bushings and mandrels tuning primer depth and or crush and so on…Not everyone has the same goal of there loads but i definitely use seating depth to fine tune after level velocities and always have a load that shoots to my expectations and i barely change during life of barrel. Either way the title of this thread is pretty vague and one could perceive its meaning in different ways.

So my view looking at this title i will say seating depth dosnt need to have a specific starting place it can be in various depths to start. Where i believe it matters and utilize it to benifit my load and accuracy is fine tuning after i level velocities. There still is a little tweaking for my expectations but certainly testing a group that shoots small can become smaller or bigger from seating depth. Everyone’s expectations are different and will have different willingness or effort to get there. Either way good luck and remember this is supposed to be fun and relaxing…… not to mention rewarding when it all works out.

 

[Harvey_NW]

Where i believe it matters and utilize it to benifit my load and accuracy is fine tuning after i level velocities. There still is a little tweaking for my expectations but certainly testing a group that shoots small can become smaller or bigger from seating depth.

Again, that is essentially the crux of this thread, you're not actually "fine tuning" anything, and the groups don't get bigger and smaller by adjusting seating depth. What you're observing is random distribution and small sample variability. Any time this theory is tested to statistical validity where a true cone of fire is established, the groups stabilize and are essentially the same size. I.E. - seating depth doesn't matter (for precision).

 

[JGRaider]

Again, that is essentially the crux of this thread, you're not actually "fine tuning" anything, and the groups don't get bigger and smaller by adjusting seating depth. What you're observing is random distribution and small sample variability. Any time this theory is tested to statistical validity where a true cone of fire is established, the groups stabilize and are essentially the same size. I.E. - seating depth doesn't matter (for precision).

You can't say with 100% certainty that he's not seeing what he's seeing. I've watched groups shrink in my 7mm08/TSX, TTSC by seating deeper, and it's unmistakable what's happening. It's a known fact Barnes mono's love some jump, as do most all copper mono's. The LRAB is known to do the same thing.

 

[greyghostnw]

You

Again, that is essentially the crux of this thread, you're not actually "fine tuning" anything, and the groups don't get bigger and smaller by adjusting seating depth. What you're observing is random distribution and small sample variability. Any time this theory is tested to statistical validity where a true cone of fire is established, the groups stabilize and are essentially the same size. I.E. - seating depth doesn't matter (for precision).

Making assumptions is a bad practice. You certainly dont know my brass prep, my tools used, my components used, my system to test and validation practices. My success with developing a redundant load for life of barrel and or brass is to my standard. My rifles shoot consistently small and bullets land where they should or i would keep testing until or take barrel off. It is simply not that hard. Testing either side 3/6/9 thousands once i like my results shows me what i need to know. Validation at many random distances and environments prove load. To each there own but argument of others you know nothing about or there practices to achieve an objective would be considered counter productive. The paper dosnt lie. If you have a meathod that works for you thats awesome. Thats the stoak one needs. If my system didn’t produce results i accept i wouldn’t bother or i would reach out to people that have success. Surround yourself with people with success equals a higher probability of success yourself. Shooters that have similar expectations or tolerences accepted are those i take pointers from. Either way enjoy the season. The hard work perhaps will reward this season. Good luck.

 

[Harvey_NW]

You can't say with 100% certainty that he's not seeing what he's seeing. I've watched groups shrink in my 7mm08/TSX, TTSC by seating deeper, and it's unmistakable what's happening. It's a known fact Barnes mono's love some jump, as do most all copper mono's. The LRAB is known to do the same thing.

Making assumptions is a bad practice.

Still not one example of valid proof. I digress.

 

[dukeball33]

I didn't read all the pages, what are folks using as statistically significant... 20, 30, 50 shot groups?

 

[JGRaider]

Still not one example of valid proof. I digress.

Why should anyone have to prove anything to you or this engineer dork? What you believe is irrelevant. I've seen it many times over 40 years of reloading, with a wide array of bullets.

 

[Castle Rock]

Why should anyone have to prove anything to you

No matter what you showed him he would just discount it anyway, his mind is made up.

 

[Harvey_NW]

I didn't read all the pages, what are folks using as statistically significant... 20, 30, 50 shot groups?

In the OP I said at least 10 shots, because that seems to be enough to apply variability to and get some expectations. Ideally "proof" would be a stabilized group, Hornady stats show that's typically 30-50, depending upon precision.

Why should anyone have to prove anything to you or this engineer dork? What you believe is irrelevant. I've seen it many times over 40 years of reloading, with a wide array of bullets.

You came to my thread, with no proof. Ironic.

No matter what you showed him he would just discount it anyway, his mind is made up.

I would not discount valid proof. That was the ENTIRE point of starting this thread, to see if anyone had any showing they improved the precision of a load by using a voodoo method. 18 pages, none.

 

[willfrye027]

In the OP I said at least 10 shots, because that seems to be enough to apply variability to and get some expectations. Ideally "proof" would be a stabilized group, Hornady stats show that's typically 30-50, depending upon precision.


You came to my thread, with no proof. Ironic.


I would not discount valid proof. That was the ENTIRE point of starting this thread, to see if anyone had any showing they improved the precision of a load by using a voodoo method. 18 pages, none.

But “the paper doesn’t lie” and “I’ve seen it with my own eyes”…

In all seriousness I would not be surprised if some bullets do need some rough seating depth tuning. But I have no desire to shoot those bullets.

If I saw irrefutable proof of a .006 change or whatever resulting in a meaningful/valid change in precision, I’d feel about the same as if I saw Bigfoot. Like holy sheet, I guess bigfoot really is out there.

But I don’t believe in Bigfoot or tuning loads, for now.

 

[Packmansion]

Its exhausting changing the diapers of the reloading world.

 

[huntnful]

As promised, here’s my extreme seating depth test now that season is over.

Since this barrel was still shooting excellent with my N570 144 Berger load, I didn’t want to burn it up more than necessary doing this, so I switched it over to H1000 just for this test.

So this is a new bullet/powder combo that has never been down this barrel. So a good baseline for testing I think.

I loaded .010 off, .110 off & .210 off. All with 65.5gr. H1000.

Started with a clean barrel, and shot 2 foulers.





Here’s the groups, labeled in the order that I shot them. I waited 5 minutes in between groups and shot the groups as 5 consecutive shots. I dialed down 1/2 MOA after the first group landed a little high.


Here’s the velocity numbers in correlation to each depth as well.


30 shots into a 1” cone across .200 seating depth difference and 56fps ES encompassing all 30 shots as well.

 

[solarshooter]

As promised, here’s my extreme seating depth test now that season is over.

Since this barrel was still shooting excellent with my N570 144 Berger load, I didn’t want to burn it up more than necessary doing this, so I switched it over to H1000 just for this test.

So this is a new bullet/powder combo that has never been down this barrel. So a good baseline for testing I think.

I loaded .010 off, .110 off & .210 off. All with 65.5gr. H1000.

Started with a clean barrel, and shot 2 foulers.

View attachment 982378
View attachment 982379


Here’s the groups, labeled in the order that I shot them. I waited 5 minutes in between groups and shot the groups as 5 consecutive shots. I dialed down 1/2 MOA after the first group landed a little high.
View attachment 982380

Here’s the velocity numbers in correlation to each depth as well.
View attachment 982382

30 shots into a 1” cone across .200 seating depth difference and 56fps ES encompassing all 30 shots as well.

Nice test!! Mean radius and T-test on the radius data pretty please? Or if you give me the x/y coords of each shot I'm happy to do it for you.

 

[huntnful]

Nice test!! Mean radius and T-test on the radius data pretty please? Or if you give me the x/y coords of each shot I'm happy to do it for you.

This is me doing my best to overlay each group for the MR. It’s pretty damn close.

 

[solarshooter]

This is me doing my best to overlay each group for the MR. It’s pretty damn close.

View attachment 982387

OK, this is one way to do it, maybe a little imprecise. Kind of seems like 0.25moa adjustment wasn't applied to the second 2 groups?