Seating depth vs. Charge Weight

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BJung

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What is your opinion on charge weight and seating depth? I know there's a youtube topic that says the distance for the lands doesn't matter. From my own experience it looks like the proper charge for a given seating depth is key. So, for example I assemble a testload with the bullet seating out as far as I can. Then, I find an accuracy load for it. But, if I seat the bullet deeper, pressure will increase. And yet, if I decrease the charge, I will return to an optimal accuracy load. Whether it would be more accurate or less from the first seating depth/charge, I don't know. What is your experience about this? Attached is a photo of a 38-148 WC test I did that supports my reasoning.
 

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What is your opinion on charge weight and seating depth? I know there's a youtube topic that says the distance for the lands doesn't matter. From my own experience it looks like the proper charge for a given seating depth is key. So, for example I assemble a testload with the bullet seating out as far as I can. Then, I find an accuracy load for it. But, if I seat the bullet deeper, pressure will increase. And yet, if I decrease the charge, I will return to an optimal accuracy load. Whether it would be more accurate or less from the first seating depth/charge, I don't know. What is your experience about this? Attached is a photo of a 38-148 WC test I did that supports my reasoning.
Interesting and @LiveLife posted some detail on a fairly recent post you may find helpful. I’ve searched for the thread and just can’t find it, but I know he’ll be able to.
 
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So, for example I assemble a testload with the bullet seating out as far as I can. Then, I find an accuracy load for it.
How do you find “an accuracy load”? Do you shoot a ladder and review the group size? I’m just curious if you have velocity data to go with it.
 
If OP's question is about pistolas, can't help.

I am developing some opinion on rifles.......currently have some loads waiting to be fired to finish the test.
 
I think you are just finding that particular cartridge in that firearm isn't that sensitive to COAL, but you've honed in on the sensitivity to velocity. I load for good enough and shoot gongs and don't really keep refining and squeezing for more and more accuracy. Initially it is relatively easy to test and find something that works good, and to refine that further and further becomes more technical and the testing needs to be more methodical, so - to me I just get to a point where it does what I want and good enough.
 
For almost all rifle bullets: Charge weight is 10x bigger knob, at least, than seating depth.

For many rifle bullets: seating depth isn’t even a perceptible knob for most shooters - especially not perceptible for most applications. Such, charge weight would be 100x or 1000x larger knob for these bullets, to the point it’s no longer worth even tweaking seating depth. Juice ain’t worth the squeeze.

Charge weight first, then seating depth. Don’t overthink the change in pressure - this is GROSSLY overstated online. Yes, crushing a 9mm Luger bullet back into the case on a feed ramp can cause pressure issues, but that really doesn’t relate to rifle loads. You’re not going to move your velocity/barrel time node by changing your seating depth. Pressure change really only matters when we seat LONGER and touch the lands. Moving away offers no perceptible change. Charge weight first, then seating depth - maybe, if you feel you even need to tweak seating depth.

Shooting one hole groups in the 1’s to 3’s, I typically do not tweak my seating depth in my match rifles. Just charge weight.
 
How do you find “an accuracy load”? Do you shoot a ladder and review the group size? I’m just curious if you have velocity data to go with it.
For rifles I shoot a ladder test and cross my fingers because I'm limited on powder. If a pattern shows, I'll take it as a trend to go in that direction. An OCR test would be better and to me only looks like a series of 3 load of the same charge weight and combined to a ladder test. I just have to save powder and am willing to take the risk and waste time. For handguns, I shoot groups to decide which load is best. My chronograph isn't reliable so I don't have velocity data.
 
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If OP's question is about pistolas, can't help.

I am developing some opinion on rifles.......currently have some loads waiting to be fired to finish the test.
Can you share what your opinions are? I always looking to learn something new out of curiosity.
 
For almost all rifle bullets: Charge weight is 10x bigger knob, at least, than seating depth.

For many rifle bullets: seating depth isn’t even a perceptible knob for most shooters - especially not perceptible for most applications. Such, charge weight would be 100x or 1000x larger knob for these bullets, to the point it’s no longer worth even tweaking seating depth. Juice ain’t worth the squeeze.

A concern of mine about seating depth is the increased pressure. My current accuracy load used an OAL of 3.100" because the bullet was closest to the rifling and could still fit in the magazine. I did not shoot this accuracy load confirm if it could shoot a tight group as possibly indicated by the ladder test. This test will and I skipped shooting for groups yet because I'm almost out of powder. I did shoot three rounds with this load and OAL at 300 yards and two of the shots fell 1" apart. It could be luck but I consider it a sign. Back to bullet seating. My current testload has rounds seated to 3.00" which is what was recommended in the Hornady manual for their bullet. I don't think 0.1" will make a difference because the current load is close but not at the maximum pressure and this is an early production Arisaka.
 
What is your opinion on charge weight and seating depth? ... looks like the proper charge for a given seating depth is key ... find ... accuracy
Determining most accurate charge vs seating depth is similar for pistol load development as rifle load development:
  1. Determine the longest Max/Working OAL that will work with your barrel/firearm and magazine
  2. Reference all available published load data to determine initial powder work up start/max charges
  3. Identify powder charge that produces smaller groups (I use known accurate reference loads for comparison)
  4. If not at max charge, incrementally decrease OAL (Say by .005") and if group size decreases, use shorter OAL. If not, use longer OAL
I assemble a testload with the bullet seating out as far as I can. Then, I find an accuracy load for it. But, if I seat the bullet deeper, pressure will increase.
This is pretty much similar to load development process I use outlined above.

if I seat the bullet deeper, pressure will increase ... if I decrease the charge, I will return to an optimal accuracy load. Whether it would be more accurate or less from the first seating depth/charge, I don't know. What is your experience about this?
Don't draw any conclusion based on those groups. If you're going to approach this seriously, you'll need lots of rounds in your groups.
As others posted, steps #3 and #4 may need large enough sample size and multiple range sessions to confirm/verify true accuracy.

We are conducting load development to reduce/eliminate reloading variables but there are shooting variables to factor also. We must conduct range tests carefully so small changes we are making with reloading variables can be seen on target (Remember, "Holes on target speak volumes"? ;)).

If we can't see the changes to reloading variables on target, then shooting variables (Including shooter input on trigger/grip and fatigue) could be overshadowing changes to reloading variables.

This is why I always take known accurate reference loads with me to the range during powder work up to compare the accuracy of rounds I am load developing. If accuracy trends of new load's powder work up is better than my known accurate reference load, then I KNOW it's not shooting variables/shooter input. If I am shooting known accurate reference loads poorly as powder work up loads, then I know it's the shooter having a bad range day. ;)
 
Don't draw any conclusion based on those groups. If you're going to approach this seriously, you'll need lots of rounds in your groups. Here's why:

https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group/

https://www.ssusa.org/articles/2021/2/17/accuracy-testing-how-many-shots-in-the-group

I understand where you are coming from. IPSC and Bullseye competitors would agree with you. But my time and money and resources are very limited. I try to achieve the best with what I have.
 
LiveLife. How small of a load variable to you use. First, I assume, we are by now working within a node to find the best load. Most of us have tools that are crude at best. They could vary by 0.1gr unless we have access to a lab scale. Do you shoot a series of groups or shoot and OCR to find your best load? Do you load is smaller increments of say 0.2gr to fine tune your accuracy load?
 
LiveLife. How small of a load variable to you use. First, I assume, we are by now working within a node to find the best load. Most of us have tools that are crude at best. They could vary by 0.1gr unless we have access to a lab scale. Do you shoot a series of groups or shoot and OCR to find your best load? Do you load is smaller increments of say 0.2gr to fine tune your accuracy load?
While I have refined pistol load development, for rifle load development, there's the additional factor of barrel harmonics/timing so you must also determine what powder charge(s) will allow the bullets to exit the barrel when the muzzle vibrates right at bore line, which we call accuracy nodes as there can be two nodes during powder work up.

For refining rifle load development, check out this "Advanced Reloading ... Rifle..." thread - https://www.thehighroad.org/index.p...s-and-discussions.778221/page-2#post-10938613

And German Salazar's archived journal for 1000 yard load development (Be patient as archived pages load slow) - https://www.thehighroad.org/index.p...s-and-discussions.778221/page-2#post-12095881
 
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LiveLife. This is slightly off topic but I'm assembling loads for my Makarov today. I've already assembled testloads using AA2 and thought that Bullseye might be better for the 95gr XTP bullets I'm using. Do you have an opinion on this?
 
LiveLife. This is slightly off topic but I'm assembling loads for my Makarov today. I've already assembled testloads using AA2 and thought that Bullseye might be better for the 95gr XTP bullets I'm using. Do you have an opinion on this?
I had a Russian Makarov chambered in .380Auto that I reget selling.

While both powders will work, particularly being small flake/ball powders to meter well, my guess would be AA No 2 will produce slightly more accurate loads ... That is IF you can shoot the difference.

And if you are looking for higher velocity loads, you need to chrono them.
 
I understand where you are coming from. IPSC and Bullseye competitors would agree with you. But my time and money and resources are very limited. I try to achieve the best with what I have.

If the testing is not rigorous, then our time and money and resources are wasted. Nothing is worse than coming to a false conclusion. We want to have confidence in our results and conclusion. We do this by increasing the shot count.
 
While both powders will work, particularly being small flake/ball powders to meter well, my guess would be AA No 2 will produce slightly more accurate loads

What is the assumption you're making here that predicts A#2 will be more accurate? Just curious about the train of thought. Thanks.
 
Basis for my opinions?

For starters, compared to most around here, I consider myself a newb......but getting up to speed as best I can. My goal is to load accurate ammunition for hunting purposes, and by accurate, my goal was 1 MOA for the 5 rifles I currently load for. Am close to that or better for most. So far, those that are good have been accomplished with nothing more than the right charge weight. Seating depth nothing more than close proximity to COAL used in load data.

Newbs can read any of several manuals, but past the basic process, most manuals will fall short of a defined load development process for accurate ammo. They take you up blind alleys, bounce around with stories, etc. but the load development process generally falls back to start low and work you way up to the max. Beyond that, they don't say how.

So next step for a newb is to go online where you find out optimal charge weight, etc. which explains more of the how of load development. Increments and such, but there are lots of variations on the variations. How big are your steps? In short, when you pull back the curtain to get a look at the wizardry going on, you discover there are all manner of variables that can affect results, and most of us cross thread so many of them, it's nearly impossible to sort out what causes what and why.

But as to optimal charge weight, what floats to the top as plausible theories.......plausible to me anyway.......is once you find a sweet spot......for whatever reason.......you hit an accuracy node. It shows up in chrony speed and it shows up on the target.

Take this target for example:

IMG_0519.jpg

That is a 15 shot load ladder, with target set at 200 yards. Powder loads increased in increments of 0.2 grains. As groups go, not too impressive, except for that group from loads 7, 8, 9 and 11. Random or an accuracy node? Chrony had those 4 or 5 shots all running about the same speed, so by all accounts, an accuracy node. How would you find it except for loading and shooting it? And that too, with random seating depth, no where near the lands. COAL same as found in load data, and within SAMMI specs. But as for testing, what is left now is to load some rounds in the middle of that range and see if it repeats.

So what happened to #10? It flew 8 inches to the left and missed the target entirely. WTH? Wasn't pulled that I know of. So why the flier? Impossible to say, but it certainly affected the group. Could it be the bullet was the twin to another I found in the box that was a full 0.10 longer measured at the ogive? I was working on a different caliber yesterday and 10 bullets varied a full 0.010"........measured at the ogive using bullet comparator. At best, there was a range of 0.003" in the middle as most probably length. According to some, 0.003" is a seating depth accuracy node, so if concept has value, how in the world can you improve on accuracy when the bullets you are working with won't allow it? Are the fliers on us or is there a limit based on what we have to work with? And that is the gross variables......not even into sorting brass for weight, bullets for weight and length, turning necks and all the other BR tricks.

Last road I intend to go up is to see if changes in seating depth affect accuracy. Some say yes, some (on here too) say no. I'm holding off until I get to test it myself.
 
BTW on that target, had an interesting deal happen. Loads 13, 14 and 15 made a massive jump of 150 fps over the 11, 12 node. And all ran the same speed. What some say was a node left them scattered wild. That jump coincided with a 98% case fill, going to compressed load. Got the speed, accuracy fell off.

Second part, and have only seen this in one place, but was a quote from Scott Satterlee of Satterlee load development method fame. As per Scott, when working on loads.......caliber and bullet, there is an accuracy node related to speed. Regardless of powder used, amount or type......he had observed that all of them hit the sweet spot of accuracy at the same velocity.

In my case, I ran the same test above with a different powder, and best accuracy of that ladder came at the same speed.....in this case around 3,000 fps.
 
Last observation, theory has it that powder charges and seating depth both relate to barrel harmonics and timing of bullet's exit to when the residual pulse from powder ignition is as far from crown as possible. That seems plausible with a rifle with 20 inch plus barrel. Timing of a pistol with 4 inch barrel a bit more dicey.
 
Basis for my opinions?

For starters, compared to most around here, I consider myself a newb......but getting up to speed as best I can. My goal is to load accurate ammunition for hunting purposes, and by accurate, my goal was 1 MOA for the 5 rifles I currently load for. Am close to that or better for most. So far, those that are good have been accomplished with nothing more than the right charge weight. Seating depth nothing more than close proximity to COAL used in load data.

Newbs can read any of several manuals, but past the basic process, most manuals will fall short of a defined load development process for accurate ammo. They take you up blind alleys, bounce around with stories, etc. but the load development process generally falls back to start low and work you way up to the max. Beyond that, they don't say how.

So next step for a newb is to go online where you find out optimal charge weight, etc. which explains more of the how of load development. Increments and such, but there are lots of variations on the variations. How big are your steps? In short, when you pull back the curtain to get a look at the wizardry going on, you discover there are all manner of variables that can affect results, and most of us cross thread so many of them, it's nearly impossible to sort out what causes what and why.

But as to optimal charge weight, what floats to the top as plausible theories.......plausible to me anyway.......is once you find a sweet spot......for whatever reason.......you hit an accuracy node. It shows up in chrony speed and it shows up on the target.

Take this target for example:

View attachment 1114476

That is a 15 shot load ladder, with target set at 200 yards. Powder loads increased in increments of 0.2 grains. As groups go, not too impressive, except for that group from loads 7, 8, 9 and 11. Random or an accuracy node? Chrony had those 4 or 5 shots all running about the same speed, so by all accounts, an accuracy node. How would you find it except for loading and shooting it? And that too, with random seating depth, no where near the lands. COAL same as found in load data, and within SAMMI specs. But as for testing, what is left now is to load some rounds in the middle of that range and see if it repeats.

So what happened to #10? It flew 8 inches to the left and missed the target entirely. WTH? Wasn't pulled that I know of. So why the flier? Impossible to say, but it certainly affected the group. Could it be the bullet was the twin to another I found in the box that was a full 0.10 longer measured at the ogive? I was working on a different caliber yesterday and 10 bullets varied a full 0.010"........measured at the ogive using bullet comparator. At best, there was a range of 0.003" in the middle as most probably length. According to some, 0.003" is a seating depth accuracy node, so if concept has value, how in the world can you improve on accuracy when the bullets you are working with won't allow it? Are the fliers on us or is there a limit based on what we have to work with? And that is the gross variables......not even into sorting brass for weight, bullets for weight and length, turning necks and all the other BR tricks.

Last road I intend to go up is to see if changes in seating depth affect accuracy. Some say yes, some (on here too) say no. I'm holding off until I get to test it myself.
In this particular test and if I may be so bold ..shot 8 is overlapping shot 7 followed by shot 9 going away or what we call breaking out. 7-8 is your stable node shoot three shot groups at the same point of aim to confirm the overlap and barrel timing, ( when the Barrel timing is optimized the rounds all impact the same location, how small is yet to be determined) seating depth, neck tension and primer testing within this node are all part of the tuning process.
 
I had a Russian Makarov chambered in .380Auto ... While both powders will work ... my guess would be AA No 2 will produce slightly more accurate loads ... That is IF you can shoot the difference.
What is the assumption you're making here that predicts A#2 will be more accurate? Just curious about the train of thought.
That guess/assumption is based on bullseye match shooting member @ljnowell who I helped set up a new Pro 1000 new out of the box (Yes, he was impressed with .001" OAL variance I posted for Pro 1000 testing) and went on to win many bullseye matches with Pro 1000 loaded match rounds - https://www.thehighroad.org/index.php?threads/first-place-in-bullseye-league.780168/

He tested various powders and found AA No 2 to be suitable for his match loads and when component shortage hit, he switched to Clean Shot - https://www.thehighroad.org/index.php?threads/looking-for-aa-2.796752/

So as I start my restock for retirement, got some No 2 and Titegroup to compare accuracy with W231/HP-38 (And I could pick up Bullseye also along with Sport Pistol).

index.php
 
Here's my general rule for rifles, and no, I didn't come up with it, but I've found it to be useful.
If your group is horizontal , your powder charge is probably in a node. I look for the tightest and most horizontal group, then tune seat depth to try to tighten the group.
 
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