Seating depth tests

I was talking with Dok7mm today about seating depth tests. So I figured I would poll the masses and see what you guys say.

Let's say all your brass is fireformed and this is the first time you are testing this bullet and powder and you decide to do a seating depth test first thing. You start with a low end charge of powder of course.

Do you look for low ES as the first indicator of best seating depth even though the group of shots isn't tight? Do you look for smaller groups first even though ES may be a little higher? Or are you looking for both low ES and a small group right off the bat?

I know that berger recommends that you do a seating depth test at the very first of load development and they say one seating depth will out shoot the others. And you use that one to start your powder charge development.

But it seems like it could be true for ES as well if you look at it like that. You take the seating depth with the lowest ES even though it may have shot a larger group and start powder charge development.

If you start out with seating depth tests first, which do you guys do?

I dont have hardly any experience compared to most guys around here, but somebody put it this way to me recently, "seating depth tuning shrinks group sizes, and powder tuning shrinks ES" that made a lot of sense. So I loaded up a seating depth test at low charge and waiting for a good day to shoot for group size, without magnetospeed, then will go to powder tuning...first time trying it this way but if it works I'll be very happy. All my development will be at 100yds, cuz that's what I can shoot at home, but will take it out and test at 300 before I go calling it my pet load. But I do kinda think the 100yard testing eliminates the effect a high ES might have during the seating depth test, so it might not be a bad thing.

Depends on the bullet. Bergers test is way to much of a jump imo. Have yet to find a bullet that won't shoot from touch to 40 off. If you search around you can usually find people that have had good luck with certain combos. When you do find a good powder, seating is pretty obvious. I have done it both ways and you can see patterns with seating depth. Sine wave type pattern with a few printing same poi. Groups might not be great but that's where you would want to be.

I have done a lot of reloading and do a lot of longrange shooting. I'm just trying to get guys in here to chime in what they think and then debate it a bit because I find it interesting.

The seating depth shrinks group size and powder charge shrinks ES can't be entirely true in theory. Have you not ever noticed when you are load developing and say 63 Gr of H1000 shot 1.5" at 400 yards but 62 Gr and 64 Gr shot crappy? The seating depth didn't change the groups because the seating depth didn't change. The powder charge changed.

It has to be a combination of the right powder charge and the right seating depth. Just wondering how people start out when they do a seating depth test first.

Normally I start with the bullet 0.020" off the lands and work up the powder charge. Once I find a load with good velocity, tight groups and low ES and SD then I work on the seating length. A lot of cartridges IMO won't group well with a starting or low powder charge.

If you look at the Sierra manual you will see that most of their "Accuracy Load" are Max loads. Hornady states that the slow powders in the 25-06 don't start performing until you reach "90% of maximum to maximum" loads.

I usually do seating depth test while i am fire forming brass. By the time I have my brass fire formed I have my depth set and only have to play with charge weight.

I usually do it the way you do Kiwikid. My thinking on it is you can most likely do it both ways that I mentioned above and come to the same conclusion and find a load. It's a lot to take in when you think about all the different variables that go into getting An accurate load.

Rflamm250 said:

I usually do seating depth test while i am fire forming brass. By the time I have my brass fire formed I have my depth set and only have to play with charge weight.

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yessir, but when you do that, are you looking for group size or low ES to determine your seating depth?

I do pretty much the same as Korhil, I start at .010 off and work backwards.
I do all my seating depth and final powder charge test at min. 500 yards.
If I'm not getting the results I'm after then I also do a primer test.
I dont let E.S be my end all, the paper target decides it for me.

As an example I worked up a load for a new 25-06 with Norma brass, Sierra 100gr Pro Hunter set 0.020" off and Rel 23. My first load was 51 gr and at 100m it grouped 3 shots into a 2" group, yuck!
52 gr was 0.583", well that's an improvement. 53 gr tucked three into 0.269", now we are talking! For some reason I had also loaded 5 rounds at 54 gr and they shoot into 0.379" at 100m. For the life of me I can't imagine the 2" 51 gr load shrinking simply by altering the seating depth.

I have a Chrono but do all load development at 400 plus with out it. So I am looking at groups. Typically if I can get a repeatable 1inch or less group at 400 it will be good out to 1k, done. I will stick the chrono on after just to get a close number to put into a calculator. Tried using a chrono looking for low es and all that jive but found that the magspeed opened groups up on lighter rifles. Just what works for me

kiwikid said:

Normally I start with the bullet 0.020" off the lands and work up the powder charge. Once I find a load with good velocity, tight groups and low ES and SD then I work on the seating length

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I kinda do this too. I start off at .020 off (CBTO) and manipulate the charge first. If I achieve 1/4 to 1/2 MOA out to 300, I never even mess with seating depth again, other than to chase the throat. The closest I've ever seated anything is .015 off. Maybe I'm wrong, but the way I look at "closer but not too close" is better as a general rule. In my opinion, neck tension, concentricity and case prep uniformity play more significant roles in tightening groups up than the "jump". It's the last variable on my list of things to manipulate.

Rflamm250 said:

I have a Chrono but do all load development at 400 plus with out it. So I am looking at groups. Typically if I can get a repeatable 1inch or less group at 400 it will be good out to 1k, done. I will stick the chrono on after just to get a close number to put into a calculator. Tried using a chrono looking for low es and all that jive but found that the magspeed opened groups up on lighter rifles. Just what works for me

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This is pretty much where I'm at. I don't look TOO hard into the numbers as the bullet tells me more than the numbers do, and I have to shoot the ammo anyways.

Seating results and ES/SD are unrelated, until best seating hits the lands (IF best seating is in the lands).