Load development with SEATING DEPTH first

[Ned Ludd]

I have performed a "coarse" seating depth test such as you described above on a few occasions when I had no idea whatsoever where a new bullet I was testing might want to be seated. In that event, QuickLoad makes it easy to choose a charge weight to use that is slightly reduced, but not so low as to make any results you find almost meaningless. Once you find the approximate neighborhood where the bullet wants to be seated, move on to charge weight optimization. It is important to note that even after doing an initial "coarse" seating depth test, I will always come back after the charge weight optimization and do a fine increment seating depth test (.003" increments) to ensure using the optimal charge weight the bullets are seated where they need to be.

To some extent, these steps in the reloading process are like the "chicken or the egg" question. Optimizing charge weight by some methods, such as OCW, will be made much more difficult if you randomly choose an initial seating depth where the chosen bullet groups extremely poorly. Likewise, attempting to find an optimal seating depth if the charge weight/velocity of your load is off from where it will actually end up by 50 to 75 fps (or more) may also be of limited value. That is why there is nothing wrong with starting out with a coarse seating depth test, then proceeding to charge weight testing, and finishing up with a fine increment seating depth test. You're attempting to optimize two interdependent variables, so you bounce back and forth between tests for one variable or the other, narrowing in on the sweet spot a little more with each test.

 

[mikecr]

"I was shocked" when one of my barrels "loved" the bullet .050 off the lands. It was a mistake when this happened, I didn't mean to set them .050 off. This barrel remained a "tac" driver until I wore it out! I did set it back and had my original results for another 1,200 rounds or so.

This is normal.

For those who pull a seated depth out of there butt, or simply set VLDs into lands and go right into powder testing, this may be common but there is no reason for it to be best. Never was.
The coarse adjustment in all of this -is seating. Powder is fine. Tension even finer
To calibrate anything you go from coarse, and then to fine, and then finer still.

 

[cw308]

Accuracy in load development making powder or bullet depth is fine . Knowing your bolt face to ogive , and bolt face to datum or shoulder is important . Bolt action I would first want to know how much wiggle room is in the case and chamber measurement or your counting on your firing pin and primer to drive the case into the shoulder and at that point your jump or jam comes into play .

I like to know first , all my cases have for example .001 case headspace , then knowing what my bolt face to ogive measurement is l know what my zero is to jump or jam . Safe to start at mid-range on powder scale for the bullet your using . What distance are you loading for is also a factor. The range I shoot at is maximum 200 yards , that's the only distance I shoot so my powder charge is at the low side of the powder scale . Loading VLD bullets your into long range shooting l would think.

 

[BoydAllen]

With a new powder, the first thing that I do is to do a sort of ladder/pressure test at 100 yards. I say sort of, because I am not just looking at elevation. I am looking for how shots cluster. I drop down to a low charge that literature tells me is not too low to be safe, and load one shot per charge at an interval that is appropriate for the case volume, on cases like the .222 up through the .308 .3 gr. I shoot all of the shots on a single target, over flags, on a morning when the wind is not difficult, and continue until bolt lift tells me that I should stop. One needs to pay close attention to do this. So many time I have seen fellows who after a clear indication that a load was too hot, ignored the obvious and chambered another one. Do not do that. After I get signs of excessive pressure, I note the temperature and humidity, and the charge just below it as maximum. Obviously, a max charge arrived at in cold weather will require retesting when the temperature is significantly warmer. At the end of the test I will usually have a target with some clusters of bullet holes made by consecutive charge weights. At that point I will load a three shot test using the middle load of the most promising cluster. I do this with the bullet seated into the rifling by an amount that I have found good results with before, so that my maximum pressure will be worst case, since jumping with that load would result in lower pressure. After I have a charge weight, I experiment with seating depth. Generally, if I can, I do all of this loading at the range. My friends who do not, generally have to invest several trips to the range into getting to a point that I can get to in less than two hours.

 

[Hengehold]

This is normal.

For those who pull a seated depth out of there butt, or simply set VLDs into lands and go right into powder testing, this may be common but there is no reason for it to be best. Never was.
The coarse adjustment in all of this -is seating. Powder is fine. Tension even finer
To calibrate anything you go from coarse, and then to fine, and then finer still.

I find your thoughts interesting.
“Seat depth=coarse, powder charge= fine, NK tension = very fine”

I have thought of seat depth as a coarse adjustment because it is always changing as the throat grows. Thanks for you input.

-Trevor

 

[mikecr]

No, seating depth is not changing with anything. It is where you set it.
Seating is the coarse adjustment to load results because no amount of anything else opens grouping as much as the worst seated position. And the most direct path to tightest grouping is to find best seating position.

 

[Tim Singleton]

Why not do both at the same time?

 

[Boyd L.]

Question: Does anyone else here prescribe to “seating depth first’ approach to load development?

After getting mediocre results working up a 6BR load in a 28” CBI threaded to a SA 700 I’ve decided to try this route. The idea of finding the “best” group as a starting point based on seating depth removes a potential variable from muddying my already frustrated psyche.

 

[DennisH]

After getting mediocre results working up a 6BR load in a 28” CBI threaded to a SA 700 I’ve decided to try this route. The idea of finding the “best” group as a starting point based on seating depth removes a potential variable from muddying my already frustrated psyche.

Mediocre Results!

Could you go more in detail?

Curious, Dennis

 

[JFrank]

^^^+1
6 BR frustrating????

Comonman

 

[mikecr]

View attachment 1101460 Why not do both at the same time?

You're showing only a last portion of load development. That is, tweaking a chosen combination for best group shaping.
You're not showing the portions of development leading to that chosen load & land relationship [28-29gr, ITL].

As far as why not do seating and powder at the same time? It's because it's 2 changes at the same time, and would lead to a helluvalot of tail chasing with anything but a tiny/all known about 6PPC.

Imagine going right to the end(as you're implying) with something like a 260AI for distant shooting.
Full (actual) seating testing goes from ITL anywhere to .120 OTL.
Incremental powder testing for it spans 5 full grains.
Put that on a spreadsheet & consider remaining barrel life after firing so many shots.
If you plotted results of it out and posted on a big wall, you could sit in front of it and see the cosmos for what it is (chaos), and be no closer to finding best load.
You'd see big swirlies of SEATING, POWDER, CAPACITY, TENSION, BORE CHANGE, and CONDITIONS -at the same time..

 

[Boyd L.]

Mediocre Results!

Could you go more in detail?

Curious, Dennis

Varget, Re15, H4895 (among others, but primarily these).
107 SMK, 95 TMK, 107 Berger VLD (Target and Hunting).
Winchester Small Primers,
CCI 400, 450, BR
Wolf Mag SRP
Federal GMM primers
Lapua Blue Box (all load combinations)

All testing is 3 shot initial groups at 300 over flags (that I’m still learning to use). Groups or flat spots that appear promising usually get a 5 shot group or two.
Best 3 shot groups have typically been in the 1/2 MOA range but attempts to better have typically resulted in inconsistent results. 5 shot groups are larger.
Depth tuning is usually attempted in .010 increments, though I’ve tried .015 and .020 increments once a 5 shot (and occasionally a 3 shot) group appears hopeful based on group size.

 

[Richard Coody]

Well i use different methods for different rifles

If it is a hunting rifle/repeater that i need mag length rounds i use the berger method for finding seating depth. Learned this works after spending some time trying to develop loads for a..308 hunting rifle. I run OCW at mag length to find a starting load then run the berger seating depth test. Who would have thought that rifle would.like the.168 VLD hunter 0.130 off. Then i fine tune both powder charge and seating depth. Berger says the seating depth node is 0.030 wide. This target shows it. Each group is 0.010 different. This is fine tuning that 0.130 seating Depth.




Now for a target rifle i run an OCW to find a starting load with a 0.010 jam. Then fine tune both one at a time.

 

[Boyd L.]

^^^+1
6 BR frustrating????

Comonman

I know...right?!?!

 

[boltfluter]

Varget, Re15, H4895 (among others, but primarily these).
107 SMK, 95 TMK, 107 Berger VLD (Target and Hunting).
Winchester Small Primers,
CCI 400, 450, BR
Wolf Mag SRP
Federal GMM primers
Lapua Blue Box (all load combinations)

All testing is 3 shot initial groups at 300 over flags (that I’m still learning to use). Groups or flat spots that appear promising usually get a 5 shot group or two.
Best 3 shot groups have typically been in the 1/2 MOA range but attempts to better have typically resulted in inconsistent results. 5 shot groups are larger.
Depth tuning is usually attempted in .010 increments, though I’ve tried .015 and .020 increments once a 5 shot (and occasionally a 3 shot) group appears hopeful based on group size.

If you are still learning to shoot over flags I would consider doing your testing at 100 yds. Very easy to miss a condition change at 300 and ruin an otherwise good group. Generally speaking, if it will shoot at 100 it will shoot at 300. If not, the load is not correct. Just what I have experienced over the years. Good luck!

Paul

 

[Richard Coody]

After getting mediocre results working up a 6BR load in a 28” CBI threaded to a SA 700 I’ve decided to try this route. The idea of finding the “best” group as a starting point based on seating depth removes a potential variable from muddying my already frustrated psyche.

Trouble with load development in a 6br?

Target below is a starting charge weight test with varget and berger 105 hybrids jammed 0.010. Starting load 29gr to 30.2 gr. Hard to pick a winner. With a little seating.adjustment and another load test wound up at 30gr .005 off.



And the final result


http://[URL=http://s1056.photobucke...rcoody1/on target_zpsiohc9gxw.jpg[/IMG][/URL]

 

[DaveTooley]

This how I've done it for as long as I can remember.
rifle #1 hunting rifle- new to me caliber
rifle #2 target rifle
I take all my loading equipment to the range.

rifle #1 I take one powder and 3 or 4 bullets to the range. All brass been sized and primed prior to going to the range . If the magazine allows I start with my preferred bullet just touching the lands. That's land marks half as long as they are wide. No chance of sticking a bullet and dumping powder.
I take one case, resizing as I go and increase the powder charge until I reach a load that is on the warm side. That load I consider my max pressure load. @200 yds. I start shooting two shot groups while seating the bullet .005" deeper each group. Almost without fail pressure will drop to a point that I have to increase the powder charge. After a series of two shot groups I evaluate performance. Did anything shoot well? Was there a pattern? If the answer was nothing shot well and there was no indication of improved accuracy anywhere in the test I move on to another bullet and start over again.

rifle#2 target rifle, new barrel, caliber/chamber I'm familiar with. One powder and two bullets. I start with an abbreviated seating depth test with a known powder charge and my preferred bullet. I may do the same test with bullet #2 hoping to find a magical combo. I also want to establish my load window which is dependent on temperature. If I tune in cool weather and summer is right around the corner I want to stay on the low side of the window so as not to get ambushed with higher pressures by a temperature spike. What usually happens is while driving to the first match in the spring, about half way there I start thinking I needed another .7 grs. of powder.

I've never subscribed to the idea of tuning by changing the powder charge as my primary tool. Using seating depth changes has always been more predictable and productive for me.

I forgot to add that once I have a load identified either rifle I then confirm with follow up with several groups of anywhere from 3 to five shots and 3-5 groups.

 

[bsekf]

Just for those using the "Berger" method.

After you get the coarse seating depth and go on to powder charge. After finding the powder charge, how much do you end up tweaking the "coarse" seating depth, several thous. or several hundreds? Then do you go back and tweak the powder charge again?

Do you find all the very low drag bullets, Nosler, Hornady and Berger, all end up with about the same coarse seating depth?

Bill

 

[Tim Singleton]

You're showing only a last portion of load development. That is, tweaking a chosen combination for best group shaping.
You're not showing the portions of development leading to that chosen load & land relationship [28-29gr, ITL].

As far as why not do seating and powder at the same time? It's because it's 2 changes at the same time, and would lead to a helluvalot of tail chasing with anything but a tiny/all known about 6PPC.

Imagine going right to the end(as you're implying) with something like a 260AI for distant shooting.
Full (actual) seating testing goes from ITL anywhere to .120 OTL.
Incremental powder testing for it spans 5 full grains.
Put that on a spreadsheet & consider remaining barrel life after firing so many shots.
If you plotted results of it out and posted on a big wall, you could sit in front of it and see the cosmos for what it is (chaos), and be no closer to finding best load.
You'd see big swirlies of SEATING, POWDER, CAPACITY, TENSION, BORE CHANGE, and CONDITIONS -at the same time..

Yep
And I can see it all on the same piece of paper
Works pretty good for me too
I think I'll stick with it

 

[dcali]

I have not found that vld bullets behave any differently than tangent ogives, but many say they’re more sensitive.

As for the “berger” test, what I’ve seen is that there is usually more than one optimal depth, often about 100 thousandths apart. Pick one of those and hone in on the best depth. 30 thou steps are pretty coarse, but you can usually get a decent idea. Usually it makes sense to go with the shorter jump because 100 thousandths has a significant impact on pressure. But there might be reasons for o the shorter depth (if your freebore is on the long side of usable, for example).

It helps to plot on a chart - group size vs jump - you’ll see what looks vaguely like a sine wave, and it should be pretty quick to get it pretty close to optimal.

The biggest help in dialing in seating depth is to load all your rounds long and do final seating at the range with an arbor press. It will save you a lot of effort, time, and money.

Once I’m within 5 or so thousandths of optimal, I call it good enough and dial the rest in on a tuner. I’ve found that if you do this, any reasonable charge weight will work. In other words, pick a powder and charge that will fill the case, burn completely in your barrel, gets near max pressures, and good velocity. Quickload is very helpful for this.

Take all the above in the context of f class. I’m not chasing the last few .001 MOA, but I am chasing repeatable groups in the .2s and .3s with my .308.