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Does seating depth eventually repeat small groups and what is good increment?

I'm developing a 6.5 Creedmoor load with a new bullet and I am working on the seating depth. I was wondering if the seating depth repeats itself so to speak as far as gets small than grows in group then gets small again, kinda like varying powder does. I usually use for powder varying 0.3 grains and I feel I don't miss where the small group happens. What is a good increment for seating depth so I don't miss it, but don't wear out my barrel and waste a bunch of ammo either?

Lastly, I hear someone can optimize powder based on ES/SD rather than group size, then work seating depth to make the group small, as if they are almost independent of each other. Anyone have any comment to this philosophy? Thanks for any wisdom that can be given :)

Don
 
I have had groups open and close again as seating depth changes. There are likely several accurate seating depths just like there are various powder nodes. Just my opinion.

ES/SD can be misleading as far as accuracy goes. While everyone strives for low SDs, I've noticed that some of my best groups lacked low SD and some of my worst groups had SDs of 1.5-4. If shooting at a consistent distance, I think consistent group size outweighs low SD. But it's hard to discount velocity spread when shooting over various (or long) distances, like hunting.
 
According to Erik Cortina the seating depth nodes do repeat app. .006 to .009. His theory is that some of these nodes are wider than others and will show small groups continuously for maybe two or three settings in a row. He also states it is best to settle on a setting in the middle of that wider node range and not settle with that one small group area of seating depth spectrum.


 
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I have found that they are about .030 apart. Let’s take a 180 hybrid. Usually 10-20 off shoots. If it doesn’t next one back is .040-.050. It’s a wave pattern similar to powder. You’ll see it come in and then group well then go out. I personally shoot Bergers and take the 180 at -.015. If this isn’t accurate I will move deeper in larger jumps. Find something coming together and I’ll test either side of that.
 
Here is where a lot of threads go into swirl because the shooting world has a variety of contexts where the answer for a heavy section barrel on a stiff action in a stiff stock, is different than the answer for a thin flexible barrel in a flimsy action and a flexible light stock.... so keep in mind that some answers are based on one end of the spectrum or the other.... Carry on... YMMV
 
Here is where a lot of threads go into swirl because the shooting world has a variety of contexts where the answer for a heavy section barrel on a stiff action in a stiff stock, is different than the answer for a thin flexible barrel in a flimsy action and a flexible light stock.... so keep in mind that some answers are based on one end of the spectrum or the other.... Carry on... YMMV
+ 1
 
I have found that they are about .030 apart. Let’s take a 180 hybrid. Usually 10-20 off shoots. If it doesn’t next one back is .040-.050. It’s a wave pattern similar to powder. You’ll see it come in and then group well then go out. I personally shoot Bergers and take the 180 at -.015. If this isn’t accurate I will move deeper in larger jumps. Find something coming together and I’ll test either side of that.
Sam Millard @ Panhandle Precision has a video on U-tube as well where he talks about seating depth at great lengths and he says he can find acceptable seating depth nodes @ .010 increments.
 
I've done alot of shooting in the last 20 yrs. From mid range f class and more recently the benchrest game. I've tested about everything a person can test. I've found seating depth window to be usually around .006 wide. But now we're talking apples to oranges when talking long range and benchrest. In long range once I found we're a given bullets like to shoot I hardly ever move it for the life of the barrel. Benchrest shooting I may move in or out what ever is needed to stay in tune. I know I just tested a new load of hottenstein bt bullets in my ppc and shot dots with a .006 swing in seating depth. Started at touch and went .003 in and .003 out and all shot dots. Bit when it open up it open up. Test and find what works best with your rifle and chamber.
 
I've done alot of shooting in the last 20 yrs. From mid range f class and more recently the benchrest game. I've tested about everything a person can test. I've found seating depth window to be usually around .006 wide. But now we're talking apples to oranges when talking long range and benchrest. In long range once I found we're a given bullets like to shoot I hardly ever move it for the life of the barrel. Benchrest shooting I may move in or out what ever is needed to stay in tune. I know I just tested a new load of hottenstein bt bullets in my ppc and shot dots with a .006 swing in seating depth. Started at touch and went .003 in and .003 out and all shot dots. Bit when it open up it open up. Test and find what works best with your rifle and chamber.
This definitely seems to be in line with what Erik is saying in the videos above. But as mentioned in the thread every rifle will like something different. It pays to test each barrel to see what it wants.
 
Ive been reloading hunting ammo for many years and just now getting into the finer details of ladder tests and seating depth tests for my attempt at long range shooting. I sure dont have a clue yet but have opted to try the method on the Berger bullet website. I think if I tried every test method I have read about in the past year I would be out of reloading components real quick.
 
My results have been that yes they come and go and come again, with magnum hunting rifles, light weight hunting rifles, varmint rifles, and Benchrest rifles. I have thousands more rounds worth of experience tuning bench guns, for obvious reasons. With them I typically find one clear winner that will compete at the level I need. Although they will still have nodes coming and going as I keep going more and more jump. I wouldn't say in all cases, but my experiences have been that nodes get bigger the more I jump. Seems to me they get further apart as they become larger windows....but I've never ran a bench gun out there, as it seems to induce a bit of horizontal when you tune out the vertical, and that adds up to midpack but consistent lol.

Tom
 
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I have had groups open and close again as seating depth changes. There are likely several accurate seating depths just like there are various powder nodes. Just my opinion.

ES/SD can be misleading as far as accuracy goes. While everyone strives for low SDs, I've noticed that some of my best groups lacked low SD and some of my worst groups had SDs of 1.5-4. If shooting at a consistent distance, I think consistent group size outweighs low SD. But it's hard to discount velocity spread when shooting over various (or long) distances, like hunting.
Cortina says there are two things to precision. 1. Combustion 2. Tuning. You can have a tuned barrel shoot high SD ammo and vice-versa. This settled my brain on the issue.
 
So I watched the Erik Cortina videos......he makes a statement "seating depth will tune any load"...sounds reasonable......so if I pick a powder load for good SD/ES, then regardless of the group size of that load, the thought is seating depth will bring it in....I'm going to give that philosophy a whirl and see how that turns out

Don
 
So I watched the Erik Cortina videos......he makes a statement "seating depth will tune any load"...sounds reasonable......so if I pick a powder load for good SD/ES, then regardless of the group size of that load, the thought is seating depth will bring it in....I'm going to give that philosophy a whirl and see how that turns out

Don

Eric has quite a surprise in this video when Speedy tests the seating depth of Eric’s ammo.
Finding a way to measure a baseline (jamb or touch doesn’t matter as long as it’s repeatable) is critical.

After watching Speedy in the first video, I decided compare that method to the way I normally check touch. I came up with a .002” difference both are extremely repeatable. One method is referenced off the case head, the other off the shoulder. In my opinion, both are very good methods to get a repeatable touch point.
Good luck, keep us posted.
CW
 

Eric has quite a surprise in this video when Speedy tests the seating depth of Eric’s ammo.
Finding a way to measure a baseline (jamb or touch doesn’t matter as long as it’s repeatable) is critical.

After watching Speedy in the first video, I decided compare that method to the way I normally check touch. I came up with a .002” difference both are extremely repeatable. One method is referenced off the case head, the other off the shoulder. In my opinion, both are very good methods to get a repeatable touch point.
Good luck, keep us posted.
CW

I've been doing "touch" and shooting into the lands .003" for the past couple years. I thought I was shooting "at touch" but later realized my shoulder is bumped back .002-.003" and upon firing it moves forward that amount along with the bullet.

One doesn't need to remove the barrel from the action. This same procedure can be done with muzzle up and gravity to check touch. If the bullet is stuck into the lands, one can use a cleaning rod to unstick. I can hear a distinctive hollow sound through the barrel when the bullet isn't touching the lands.

A faster method yet is to use a wooden dowel rod , or coated cleaning rod. Slide the round in with a finger. Use the dowel rod from the muzzle end to unseat the round stuck in the lands. If one wants to get super duper precise, use a new bullet after you found touch just in case the previous bullet got engraved a bit by the rifling.

I'm surprised Speedy kept saying the barrel has to be removed from the action. This is just simply not the case. Is it slightly more convenient to just be working with a barrel out of action, but that is about all the benefit.

Anyway, I am getting great accuracy/precision in all the guns I've set .003-.005" into the lands.
 

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