Which comes first - charge weight or seating depth?

[Newtosavage]

After handloading for a couple years, I truly appreciate the difference in accuracy a small change in charge weight or seating depth can make. Normally, I start with working "up" a charge weight while shooting 3-shot groups, then I adjust seating depth for groups.

Today, I was wondering though, is that backwards? I mean is there any merit to searching for the best seating depth first since it can affect the pressure, then tweaking the charge weight?

 

[nettlle]

I am sure everyone's method is different but I always worked up loads with the best possible combination of powder and bullet as these two components always had the biggest affect on accuracy. After settling on the bullet and powder I would then experiment with seating depths.

 

[FROGO207]

I will make sure the seating depth I have chosen will fit the mag, cycle, and plunk without hitting the lands, especially with hand gun ammo. Then it is on to load development with charge weights and/or different propellants. THEN I will fine tune seating depth if needed. Never been disappointed with my results in 30+ years of reloading YMMV.

 

[z7]

To avoid pressure issues seat bullets long when doing a workup (rifle that is) i set them to kiss the lands if possible, or set to the longest workable oal for the magazines

When you adjust seating depths you are backing the bullet away from the lands, and are dropping pressure by giving it more jump

 

[Newtosavage]

I think for the next year or so, I'm going to pick a mid-range load out of the data, then start with seating depth and then experiment with charge - in that order. A little nagging voice is telling me that is going to save me some time in finding the most accurate load for each bullet and powder combo.

 

[someguy2800]

I do charge weight first. My order of importance for accuracy in rifles goes as follows

1. Bullet type
2. Powder type
3. Charge weight
4. Seating depth
5. Primer type

If you have the first 2 right everything just kind of falls in place and the next 2 make relatively minor differences. I only mention primer because some powder seam to work much better with hotter or softer primers. Most of my guns are hunting rifles with hunting bullets that you can’t get out to the lands so it’s not that big a deal in my experience

 

[Bfh_auto]

I use a ladder test if I can find the lands.
If I can't reach the lands, I seat to mag length and find the optimal powder charge.
Lately I've been playing with plated bullets and shotgun powder. Fast powders don't seem to care about seating depth as much.

 

[LiveLife]

Normally, I start with working "up" a charge weight ... then I adjust seating depth for groups.

is that backwards? I mean is there any merit to searching for the best seating depth first since it can affect the pressure, then tweaking the charge weight?

No, you got it right.

I do the same:

1. Determine working OAL/COL
2. Conduct powder workup to identify accuracy nodes
3. Once most accurate powder charge(s) are identified, I incrementally decrease OAL to see if accuracy improves.

I use the same process for both pistol (semi-auto) and rifle load development.

 

[Walkalong]

1. Bullet type
2. Powder type
3. Charge weight
4. Seating depth
5. Primer type

Hard to find fault with as far as rifle goes.

If I am loading to fit the mag, then seating depth is fixed. Bullet, powder, charge weight. It may prefer one primer over another.

 

[Walkalong]

With pistol I crimp into a cannelure or crimp groove or pick an OAL that feeds 100%. After that it is try powders and weights. Bullet is still number 1. Primers generally make small differences if at all.

 

[Newtosavage]

I do charge weight first. My order of importance for accuracy in rifles goes as follows

1. Bullet type
2. Powder type
3. Charge weight
4. Seating depth
5. Primer type

If you have the first 2 right everything just kind of falls in place and the next 2 make relatively minor differences. I only mention primer because some powder seam to work much better with hotter or softer primers. Most of my guns are hunting rifles with hunting bullets that you can’t get out to the lands so it’s not that big a deal in my experience

I would agree except that lately I've found that a few of my favorite bullets do better (in some cases MUCH better) with a jump than they do seated near the lands. For example, I backed my 162 ELD-X's off from 2.94" (0.020" off the lands) to 2.90" and they really came to life. Nearly shrunk my groups in half and they were good to begin with. I backed off my 139 SST's from 0.020" off to nearly 0.150" off and the groups shrank significantly. Meanwhile, if I don't put my Berger VLD's within 0.020" of the lands, the groups open up quite a bit. So at least for a few bullets, seating depth is more important than powder OR charge.

 

[PhillySoldier]

Since changing the seating depth in itself can change the pressure/velocity of the round; does anyone change the charge weight as they change seating depths to maintain the same velocity?

 

[labnoti]

To avoid pressure issues seat bullets long when doing a workup (rifle that is) i set them to kiss the lands if possible, or set to the longest workable oal for the magazines

When you adjust seating depths you are backing the bullet away from the lands, and are dropping pressure by giving it more jump

How does more jump result in less pressure than providing the expansion space to begin with? If the bullet were set deeper in the case, the gas would have less space to expand before it also had to push the bullet out as far as it would already be if it were seated longer. The friction of the lands has to be overcome in either case. Is the friction more in one case than in the other?

 

[otisrush]

I essentially do them in opposite order when working up rifle vs pistol.

For rifle I once read (probably here) that charge is the big knob, and seating depth is fine-tune adjustment. So I pick a distance off the lands (such as .015) and load up various charges at that constant jump. Then, whatever groups the best out of those, I then load test loads at that charge, but with varying jumps.

For pistol I first determine what depth I need to have in order to plunk, and then try different charges to see which one performs best.

 

[someguy2800]

How does more jump result in less pressure than providing the expansion space to begin with? If the bullet were set deeper in the case, the gas would have less space to expand before it also had to push the bullet out as far as it would already be if it were seated longer. The friction of the lands has to be overcome in either case. Is the friction more in one case than in the other?

A jump gives the bullet a running start to engrave the rifling. Having the bullet jammed in the rifling is like trying to push a nail into wood by just setting the hammer on top of it and pushing. Its a lot easier with a little momentum.

 

[Demi-human]

Straight walled cartridges are more sensitive to seating depth than a bottle necked cartridge. Moving the bullet in on a rifle(bottle necked) cartridge has less effect because it displaces less case volume than if one was just 'shortening the tube', so to speak.

I like the truck tire and curb comparison. Its hard to get going bumped up to the curb. Its easier to start when it's rolling.

 

[Sofie007]

https://www.google.com/search?q=int...8#imgdii=OSDM5LYpE6ZRSM:&imgrc=kjK3oCxOuRuxxM:
Please refer to the graph above.
The first peak in the curve is the bullet starting to move from the rest position in the case. The second peak in curve (at about 1300 microseconds) is the pressure that it takes to overcome engaging the lands. When the bullet is resting on the lands when the round is chambered, then these two peaks will be superimposed and when the load is developed, overpressure signs will begin to manifest (e.g. difficult bolt lift, head separation, blown primer), so shooter would stop their load development at that point. Make sense?

 

[Sofie007]

Since changing the seating depth in itself can change the pressure/velocity of the round; does anyone change the charge weight as they change seating depths to maintain the same velocity?

I essentially do them in opposite order when working up rifle vs pistol.

For rifle I once read (probably here) that charge is the big knob, and seating depth is fine-tune adjustment. So I pick a distance off the lands (such as .015) and load up various charges at that constant jump. Then, whatever groups the best out of those, I then load test loads at that charge, but with varying jumps.

For pistol I first determine what depth I need to have in order to plunk, and then try different charges to see which one performs best.

After deciding on your best charge, it is safest to reduce charge (~ 5%) if you are going to change the seating depth (either increasing or reducing the jump). Less jump: risk superimposing the pressure peaks. More jump: Creating less free case space leading to exponential increase in case pressure. Remember, the case pressure is not linear as air space decreases.

 

[Demi-human]

Creating less free case space leading to exponential increase in case pressure.

Very much so in a straight walled cartridge. Not so much in a rifle, though I imagine it does have an effect. The link didn't go anywhere particularly useful to the specific idea of rifling engraving on bullets, but does show a great web-read. I have read the good father's site extensively. In fact I owe him a Grolsch right now, my pistol is on the countertop across the room.

I must disclose that I routinely seat into the rifling. Obviously with knowledge and caution.

 

[entropy]

Well, you have to throw the charge before you seat the bullet, unless you want a bullet stuck in the bore.......so I guess the charge weight comes first.
As for the practicality, I agree with frogfurr, COL is a minor adjustment compared to charge weight, I only deviate from formulaic COL data after adjusting charge weight doesn't get the result I want. (And mag length isn't an issue)