question on seating depth/ladder test

jimbires

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there is 100 different ways to skin this cat , and we all have our preferred way of reaching our accuracy goal . all you can do is give a different way a try to see if it helps short cut the process . I worked powder first for 40 years , the past few I've been working seating first . it seems I get on a good load quicker .
 

Whitesheep

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Currently I go with depth first and then charge weight. I agree that either will get you to the same place eventually, but that it also depends on the rifle.

One rifle I have is extremely sensitive to seating depth with Sierra's, but not so much powder charge. This same rifle is also powder brand sensitive. Other rifles I have are more charge weight sensitive.

I find I get to my accuracy node faster starting with seating depth, but I understand others find the opposite. In the end I believe the key is to do both and not just take COAL from the book.

What does the group think about a potential advantage of seating depth first at a mid powder weight level. If a close to lands COAL results in pressure issues, would this be less of a problem than if you started with a full power load and then pushed closer to the lands? I am think pressure is pressure, but maybe I am not thinking right.

Berger's write up is excellent especially if using their bullets.
 
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Dell

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I've always ran a ladder test to find good nodes for the powder charge and then started moving the seating depth around to find best load.

I've read that some folks start with seating depth and then find the correct powder charge.

thoughts on which is better and what charge do you use to find seating depth if you start with that?
I start with a .015 jump then start playing with various powder charges looking for consistency in group sizes. Once I hit a consistent one MOA or less at 100 with 5-7 round groups, I start playing with seating depth on the selected load. I’ll move the seating depth .002 down at a time from the starting point (.015) and shoot again for group sizes. Once I have my desired half MOA or less, and it remains consistent, I’m there. As you decrease your jump, make sure to keep an eye on any pressure issues. Anyway, that’s a system that’s worked for me for hits on steel out to a mile and one shot drops on big game out to 750 with several elk, mule deer and antelope taken in the 400-600 yard range. Lotsa good ways to achieve your goals.
 

Dell

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I start with a .015 jump then start playing with various powder charges looking for consistency in group sizes. Once I hit a consistent one MOA or less at 100 with 5-7 round groups, I start playing with seating depth on the selected load. I’ll move the seating depth .002 down at a time from the starting point (.015) and shoot again for group sizes. Once I have my desired half MOA or less, and it remains consistent, I’m there. As you decrease your jump, make sure to keep an eye on any pressure issues. Anyway, that’s a system that’s worked for me for hits on steel out to a mile and one shot drops on big game out to 750 with several elk, mule deer and antelope taken in the 400-600 yard range. Lotsa good ways to achieve your goals.
Didn’t mention it earlier but I am a big believer in monitoring and logging all your chrono data. Most of my loads are in the single digit SD’s but not all. My 7 mag, for whatever reason is never much below 14 but it is truly a tack driver at all the ranges I play with it in. It also performs best with a .030 jump. Go figure. This wouldn’t be near as much fun if it were an exact science.
 

Wolf76

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I start with seating depth first. That's one variable that can be taken off the table during the rest of load development. You can find a fps node and tweak seating and still not have optimal groups. With the right seating depth, I can watch the groups open or close based on the harmonics. A wide node is nice, but my load process is tight.
More than 1 way to skin a cat.
 

DSheetz

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I start by studying load data published by manufactures Nosler, Hornady ,Sierra , Burger ect. then I pick the powder they found to work best for them and the charge weight for it they used and the seating depth they used . I will use different powder charge weights to see what my barrel likes then start changing the seating depth . I find that some of my barrels don't like one powder or one brand of bullet no matter what powder charge or seating depth I use and that is what keeps it interesting and why some people change guns and calibers like some of us change clothes I think .
 

brettman

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I normally run a 10-15 round ladder through the chrony first, looking for 2 things: where I start to see pressure at and flat spots in the velocity readings. From there I take the center of the highest speed plateau that doesn't show pressure signs and begin running seating depth tests. First test is pretty much the Berger setup, then start fine tuning from best results. All this is usually with new brass anyhow so I don't mess with the charge until they're all fire formed. Run another couple ladders but at 3-400 after fire forming, then fine tune from there. Every once in a while I have to tweak seating after once fired but not often and usually minimal adjustments.
 

dakewlndn

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I tend to start with charge weights at a fixed COAL, either manufacturers recommended jump or longest length that will feed from the mag, and look for not just the best group but narrowest velocity spread as well. I'll usually do a velocity ladder first where I focus entirely on numbers from the chrono looking for flat spots regardless of group size. I'll then pick the fastest flat spot load up 5 rounds at each charge weight bracketing it and shoot for groups.

That will usually yield something in the 0.5MOA range with single digit SDs in my experience so I call it good at the point. Honestly, unless it is much more than 0.75MOA I still wouldnt mess with it as long as it still had single digit SDs.

Shooting bughole groups is fun for throwing shade on other people at the range or if you are a bench rest shooter, but for practical shooting disciplines and field use if you look at WEZ analysis, group size has a negligible impact on hit probability once you get below 1MOA.

Exactly what I do. I do mess with the seating depth at the end of this process if it needs to.
Trying to stay within the mag length.
 

Eric H

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Tried IMR8208 XBR in my 6.5X47 and got .2 moa at 100yds. I'm running about 2650fps. Should I attempt to increase speed or test out to 300yds with that speed?
 

Dell

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Tried IMR8208 XBR in my 6.5X47 and got .2 moa at 100yds. I'm running about 2650fps. Should I attempt to increase speed or test out to 300yds with that speed?
Sounds like you found the sweet spot. I’m guessing a 140-143 grain bullet? I’d make sure the group is repeatable at 100 then give her a whack at 300 and beyond. I’ve seen impressive results with the 140’s at distances out to a mile with what you are getting for MV and up to 2700 FPS. Shot next to a guy that hit our mile target 3 out of 3 times in a match with a custom build .260 Rem at about 2700 FPS. 140 Berger VLD’s.
 

Dell

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Sounds like you found the sweet spot. I’m guessing a 140-143 grain bullet? I’d make sure the group is repeatable at 100 then give her a whack at 300 and beyond. I’ve seen impressive results with the 140’s at distances out to a mile with what you are getting for MV and up to 2700 FPS. Shot next to a guy that hit our mile target 3 out of 3 times in a match with a custom build .260 Rem at about 2700 FPS. 140 Berger VLD’s.
By the way. IMR 8208 XBR is my powder of choice in my .308. Great stuff and switched to that a couple years ago over RL-15.
 

Eric H

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Sounds like you found the sweet spot. I’m guessing a 140-143 grain bullet? I’d make sure the group is repeatable at 100 then give her a whack at 300 and beyond. I’ve seen impressive results with the 140’s at distances out to a mile with what you are getting for MV and up to 2700 FPS. Shot next to a guy that hit our mile target 3 out of 3 times in a match with a custom build .260 Rem at about 2700 FPS. 140 Berger VLD’s.
This is a 123gr Hornady SST.
 

JMPrecision

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I have had the best results setting my seating depth at a lite touch to 003 off ,then work up to my max powder charge. Then I have my actual pressure max worst case scenario . Do a powder charge test by 3 to 5 tenths increments. Looking for the least verticle and smallest SD then tweak seating depth to fine tune. Typically yields .2 to .3 moa results
 
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