Seating depth - does it even matter?

[bmart2622]

Id say it definately has a lot to do with being a VLD, doubt you would see that kind of change with a hybrid type bullet

 

[Harvey_NW]

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.

Pretty much exactly what I've been doing too.

 

[VernAK]

I shoot a lot of Barnes TSX, TTSX and LRX and have experimented with seating depths but I finally just settled on seating all of them to the top groove regardless. It seems to work just fine!

 

[B23]

There is some theory about older chamber design vs newer playing a role in this

When you say old VS new are you referring to lead angle?

I ask because I have one rifle that has a 3° lead angle and it is pretty particular on seating depth, as in it will lay them in there with these perfect little clover leaf groups when they're seated in the happy place but during load development things would go to shooting groups measured in inches if seating depth was the only thing that was changed. I always thought that 3° lead angle had something to do with it and talked to JGS about it and they concurred.

 

[Axlrod]

Research positive compensation. Basically as the bullet moves down the barrel, the barrel vibrates up and down. Usually the best accuracy is when the bullet leaves the barrel, it is near the top of the "up and down" swing.
I start with powder charges first on a ladder at 600-800 yards. 2 of each charge, bullets colored with a marker to tell them apart on the target- I use white butcher paper. You can tell the "upswing" point of your barrel when different powder charges cluster together. After this I do a seating ladder with the powder charge that has the least vertical. Again 2 of each, colored. There will be one seating depth that is better, most of the time. All of this will be no more than 20 rounds.
Last I will do neck tension .002/.003/.004/.005. doesn't always round out that way- just depends on the bushings. But I do 4 bushings and track it by the bushing size. 2 of each. Since I have done this I have found most every cartridge/rifle combo has shot better with more neck tension, I would say .004 and up have been the best.
I have had very good success finding repeatable loads this way. Need to have calm day and at least 600 yards for it to work.

 

[Harvey_NW]

When you say old VS new are you referring to lead angle?

I ask because I have one rifle that has a 3° lead angle and it is pretty particular on seating depth, as in it will lay them in there with these perfect little clover leaf groups when they're seated in the happy place but during load development things would go to shooting groups measured in inches if seating depth was the only thing that was changed. I always thought that 3° lead angle had something to do with it and talked to JGS about it and they concurred.

Interesting. Yes, leade angle, freebore, and clearance in the throat are the factors commonly referenced.

Research positive compensation. Basically as the bullet moves down the barrel, the barrel vibrates up and down. Usually the best accuracy is when the bullet leaves the barrel, it is near the top of the "up and down" swing.
I start with powder charges first on a ladder at 600-800 yards. 2 of each charge, bullets colored with a marker to tell them apart on the target- I use white butcher paper. You can tell the "upswing" point of your barrel when different powder charges cluster together. After this I do a seating ladder with the powder charge that has the least vertical. Again 2 of each, colored. There will be one seating depth that is better, most of the time. All of this will be no more than 20 rounds.
Last I will do neck tension .002/.003/.004/.005. doesn't always round out that way- just depends on the bushings. But I do 4 bushings and track it by the bushing size. 2 of each. Since I have done this I have found most every cartridge/rifle combo has shot better with more neck tension, I would say .004 and up have been the best.
I have had very good success finding repeatable loads this way. Need to have calm day and at least 600 yards for it to work.

I have, everything I can find with data taken to a significant sample size disproves that theory and further substantiates random distribution. The key there is "2 of each charge". The ballisticians are proving that when you shoot multiple groups of 30+ at each charge, or seating depth, the sinusoidal noise averages out. I've researched Satterlee, OBT, OCW, and listened to the podcasts or watched the videos with each, and they are all based on small sample size. I'm wondering if there is a hobby reloader with a hunting rifle that has proof of at least 10 round groups, where seating depth made a distinguishable difference outside of the statistical variability. I think when Alex Wheeler takes a 300 PRC case and shoots a 20 shot string with 8" of vertical, and then shrinks it to 3" of vertical on the next string by bumping up to .005" neck tension, there might be a case to be made. But there are still environmentals involved in those groups, and I think the average shooter with a hunting rifle probably can't shoot the difference in small changes like that, IF there was even a discernable difference. And 99% don't take it to a significant sample size anyways.

 

[robby denning]

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

agreed, Jake @Unknown Munitions used seating depth to finish of my already accurate load. I believe he took me from roughly 0.75" to 0.5" using seating depth. It definitely solved my personal 3rd world problem

and was interesting

 

[bmart2622]

Bigger changes like .015-.020 changes can be beneficial and worthwhile, small .001-.005 arent worth the time and components just like 0.1 gr changes in powder charges arent

 

[Harvey_NW]

agreed, Jake @Unknown Munitions used seating depth to finish of my already accurate load. I believe he took me from roughly 0.75" to 0.5" using seating depth. It definitely solved my personal 3rd world problem

and was interesting

Nothing against Jake, but his procedure is small sample size load development as well. The .25" improvement is within the statistical variability of the distribution of almost any load, so the ballisticians claim if you were to shoot samples of 30 of both loads, there's likely no actual improvement. This is what's interesting to me, contrary to the traditional ideology of load "development".

 

[KurtR]

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.

I loaded 110 ttsx in a 270 wsm and they needed to be in the lands other wise they were very inconsistent.

 

[Bluefish]

I am sure that some chambers do benefit from little to no jump. ones that do not hold a bullet tightly may see an improvement as it can’t get as random and angle entering the lands. I have also read that throat erosion becomes an issue if you are chasing small jumps in small increments. The jump may actually change faster than you develop loads. That suggests you want a jump that is not sensitive to change. https://precisionrifleblog.com/2020/03/29/bullet-jump-load-development/

 

[Rob5589]

I loaded 110 ttsx in a 270 wsm and they needed to be in the lands other wise they were very inconsistent.

Which is contrary to most; they usually can jump a mile and still work. Every gun has it's nuances.

 

[nhyrum]

Nothing against Jake, but his procedure is small sample size load development as well. The .25" improvement is within the statistical variability of the distribution of almost any load, so the ballisticians claim if you were to shoot samples of 30 of both loads, there's likely no actual improvement. This is what's interesting to me, contrary to the traditional ideology of load "development".

If no one's testing or sample size satisfies your curiosity, and you want to know if there's an actual difference, why don't you test it yourself. Shoot 30 round test strings at various seating depths and see if what your ballisticians claim is actually true.

Sure it's a lot of components, but what's 60 rounds? It might make a difference, it might not, but it seems these statistics you're using are purely theoretical.

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[robby denning]

Nothing against Jake, but his procedure is small sample size load development as well. The .25" improvement is within the statistical variability of the distribution of almost any load, so the ballisticians claim if you were to shoot samples of 30 of both loads, there's likely no actual improvement. This is what's interesting to me, contrary to the traditional ideology of load "development".

sure, but my gun definitely shot better, so for my sample size it was a win!

 

[Ice-kub]

One would probably need 90 rounds for three groups, each one at polar opposite of seating depth ranges, correct? Start with a "consistenly small grouping" load that's somewhere in the middle of the seating depth range and one on either side? Would you shoot round Robin at three targets or all 30 from first group, second, third?

 

[robby denning]

OP

I found the thread I was referencing earlier. You can go through it yourself for free and not even have to fire a round

It took Jake and me several months to build that thread

The meat of it concerning seating depth is from pages 5 through 7.

Unknown Munitions for the 270 WSM

Man he has helped me a lot on reloading. Like you Robby, I have been reloading most of my life ( im not near as OLD as you though) but its been 20+ years or so. Jake has definitely upped my game (and lowered my bank account).

rokslide.com

 

[justin davis]

Interesting stuff

 

[rayporter]

you must always remember that all barrels are different, and you must test yours to know for sure.

sure, but my gun definitely shot better, so for my sample size it was a win!

 

[Pharmseller]

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.

.308” caliber, .30-06 cartridge.

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

The results are similar regardless of bullet, but you’re right, I haven’t seen this magnitude with Noslers or Hornadys.




P

 

[willfrye027]

Does it matter? Depends on what you want to do. The F class guys think it matters. I am a hunter first but enjoy shooting steel regularly out to 1000 and a little farther.

For a long range hunting rifle or shooting steel it does not matter if you are 1/2moa for 10 shots or 1MOA for 10 shots. Misses at distance will be from the wind, assuming you make a good shot.

After learning from Forms post, the hornady podcast, and years of reloading I have stopped chasing tiny groups because they are usually not repeatable and don’t matter.

If a bullet/powder combo is not giving me the desired performance at 1gr below pressure signs and seated at mag length or whatever depth is chosen…then I move on to another combo.

So for me, no it does not matter.