Advantages to finding seating depth before charge weight?

[Winny94]

I typically find my charge weight, then move to seating depth testing, but lately ive been reading about people finding seating depth first, then moving onto finding the charge weight (and I am a novice relaoder at best, so i am not at all insinuating anything i do is ideal). I was even told to do that process form a Berger tech. So since I consider the reloaders on this board to be the most knowledgeable I can find on the net, I want ask to what order you guys do it and why (just high level - obviously everyone can have different details for infinite reasons).

thanks for any insight

 

[RegionRat]

I think it is hard to generalize. In my mind the answer is "it depends'...

If the design is very close to a standard, and you have a rough idea of where the velocity will be and how the chamber is reamed with respect to a particular bullet, then it probably doesn't really matter what order you run those two variables.

However, if you don't have a very standardized situation and both of those variables are wide open, then my own opinion would be to set a length based on the situation such as magazine length restrictions or seated just short of jam, and then modulate charge first to find the pressure limits, and then make your decision on the question of setting seating depth or velocity first.

I'm not sure the initial charge weight is always obvious, so a standardized seating depth first guess is magazine length or just off jam. Where would someone guess a charge weight or velocity should be without testing that range... I don't know.

So when it comes close to standardized designs, it seems much easier to have a good idea of where things will end up. But not always...

 

[David Christian]

Rough powder test
Seating depth test
Fine powder test

It is really that simple. It also helps to do your fine powder testing at your planned shooting distance so that you can accurately measure vertical spread.

 

[Winny94]

Rough powder test
Seating depth test
Fine powder test

It is really that simple. It also helps to do your fine powder testing at your planned shooting distance so that you can accurately measure vertical spread.

What constitutes a rough powder test to you? 1% of approximate charge increments? ANd are you looking for any nodes at all, or strictly pressure signs?

 

[NorCalMikie]

Seating depth? All my loads are built with the bullets jammed .010 into the lands. That never changes. As the lands wear, the seating depth stays the same at .010 jam. New barrel will get measured for land depth, written down and referred to often. As the throat wears, OAL increases to a jam. I start with the lightest bullets I can get and go heavier as the throat wears.
And I have been known to open the bolt,pull a bullet on a live round and filled the chamber with powder. Muzzle is pointed up just for that reason.
What I have found over time is, a load built with the bullet jammed into the lands will not show pressure the same as a bullet with a jump to the lands. Jump to the lands, 28 grains of powder will start showing pressure. Jam into .010 and you can go up to 30 grains with no pressure signs.
Go 30 grains from the start and you may end up having to beating the bolt open.
Five shots that can be covered with a dime is what I'am after.
Hunting rounds? Maybe not but I bench shoot so it works for me. YMMV.

 

[David Christian]

What constitutes a rough powder test to you? 1% of approximate charge increments?

@Winny94, I typically load up 10 charge weights that cover a 5% span of known or estimated max charge. So, 0.5% increments for rough powder testing.

 

[JMayo]

Bench rest only for me.
Ive learned my rifle type (6brA)
I play load (touching) then play with depth. Then play neck tension then play load again !

So much playing with my toys !

 

[Paddyd]

Well, there are SO MANY variables to consider a person can go insane trying to find the "right" way to go about it. I prefer the simple method of starting with the overall length published in the manuals. I then find the powder charge that gives me the best results downrange. IF it doesn't get me at least 1/2 MOA or better, I will take the best group and then start playing with seating depth. Some get fantastic results from jamming, but if a loader isn't very experienced, he/she can get into uncharted pressures very quickly. Most people would be surprised how far a bullet can jump and remain very accurate as long as the cartridge is fairly concentric.

 

[JFrank]

The advantage of testing seating depth prior to powder would be in my opinion limited to Secant ogive projectiles, I’m no expert so just an opinion as I use a Tangent ogive and test seating second.

 

[Winny94]

The advantage of testing seating depth prior to powder would be in my opinion limited to Secant ogive projectiles, I’m no expert so just an opinion as I use a Tangent ogive and test seating second.

And what prompted me asking this question is I'm trying to find a load for a Berger 7mm vld hunter (i.e secant ojive)

 

[JFrank]

It’s my understanding that Secant ogive could have a very wide range of seating depth to choose from -010 to .130 off

 

[dsculley]

Unless you always want a jam like NorCalMikie then the Berger seating depth test first at a moderate charge. Then test for charge weight. Then a test for fine seating depth if needed. This has worked well for me for quite some time.

In my 7mm Rem Mag, the Berger hunting vld's are seated with a 0.075" jump. When I run the Berger seating depth test, the groups open up and shrink just like they do in powder charge testing. Once I find the seating depth, the groups don't open up as much when testing charge weight as they did when I used to test for charge weight first with an arbitrary seating depth.

 

[Winny94]

It’s my understanding that Secant ogive could have a very wide range of seating depth to choose from -010 to .130 off

Yea, evidently. I was doing some reading and found this is the test they recommend

Load 24 rounds at the following CBTO

1. .010 off the lands (jump) 6 rounds
2. .050 off the lands (jump) 6 rounds
3. .090 off the lands (jump) 6 rounds
4. .130 off the lands (jump) 6 rounds

 

[JFrank]

Yes
And one area will shoot much smaller than the others indicating a range to explore at .005 increments

 

[Winny94]

Unless you always want a jam like NorCalMikie then the Berger seating depth test first at a moderate charge. Then test for charge weight. Then a test for fine seating depth if needed. This has worked well for me for quite some time.

In my 7mm Rem Mag, the Berger hunting vld's are seated with a 0.075" jump. When I run the Berger seating depth test, the groups open up and shrink just like they do in powder charge testing. Once I find the seating depth, the groups don't open up as much when testing charge weight as they did when I used to test for charge weight first with an arbitrary seating depth.

thanks for the reply. Are you running the 180s or 168s? What is your definition of a moderate charge? My problem is, im shooting a 7 sherman short so there is no published data. From my research, with my powder, the starting load is ~56gr for a 180class bullet and max around 62. Ive fired 50 rounds to break in the barrel a bit with a 56gr load and 183 smks, which predictably had no pressure signs (and was surprisingly accurate).

 

[JFrank]

So what’s your plan?

 

[garandman]

Reading thru with interest.

Ive gotten to the exact powder load, then dialed in the seating depth.

It got me to 0.3 - 0.45" @ 100 yd.

Im guessing the order really doesnt matter.

But Im still reading.

 

[garandman]

I start 0.020 off the lands using a Hornady comparator.

 

[Winny94]

So what’s your plan?

Still reading, but if I had to do it today, id probably load 8ish rounds in .5gr increments from 57-61ish just to make sure pressure is safe, then pick a middle charge weight (58-59), and then run Bergers depth test. But im hoping I get a few more opinions before having to load this next batch.

 

[JFrank]

Good plan”