Seating die question

Caliber?
Weight/type of projectile?
Die brand?
Variation?

My biggest depth variations came when I was loading pistol ammo and got an excess of bullet lube up in the dies. You might check that.

Good luck.
 
depends on the die(s). Example, I have a flat and pointed seating plug for one of my
dies depending on projectile. take a peek inside the die or let us know what you're using.

Are you trimming the brass?
Do you know as fact that they are all the same length?
 
When I used to load for rifle, I had seating depth inconsistencies that affected accuracy. I found that the seater stem wasn’t drilled deep enough. The really pointy bullets and/or the polymer tipped bullets were too long and the seater stem would index on the tip of the bullet rather than the ogive of the bullet.

You can actually send Hornady your seater stem and a sample bullet and they will drill it out so that the stem doesn’t index on the tip of the bullet. So this all leads me to believe that you want the stem to index on the ogive for best accuracy. At least for pointy and tipped rifle bullets.
 
When I used to load for rifle, I had seating depth inconsistencies that affected accuracy. I found that the seater stem wasn’t drilled deep enough. The really pointy bullets and/or the polymer tipped bullets were too long and the seater stem would index on the tip of the bullet rather than the ogive of the bullet.

You can actually send Hornady your seater stem and a sample bullet and they will drill it out so that the stem doesn’t index on the tip of the bullet. So this all leads me to believe that you want the stem to index on the ogive for best accuracy. At least for pointy and tipped rifle bullets.
I wonder if this is what is happening. I'm using rcbs dies. Loading 223 hornady bthp, 68 gr.
 
Check the bullets themselves. I've had Sierra Matchking HPBT bullets with measurable length differences. It was due to how they swaged the HP closed at the tip. However, what is most important is the distance to the rifling lands. Measuring part way down the ogive gave very consistent lengths, so they were good.
 
Put some magic marker on the tip right before it gets seated. Then look at the seater stem to see if the tip of the bullet marked it
This^^, or look at the bullet to see where the ink is scratched by the seater stem.

A sharpie is a great tool to have at the reloading bench. When I didn't have the proper gauge to determine the distance to the lands in a gun I would load a bullet into an empty case, but a little long. I covered the bullet with sharpie then chambered and un-chambered it. I could see the scratches in the ink showing where the lands were touching, so I seated the bulled 0.010" further down, refreshed the sharpie and chambered it again. Rinsed and repeated until it no longer touched the lands.
 
How much is the variation ? I was told by a tech at Bergers to expect a +- of up to .003 across a lot of bullets. If you buy a box of 100, you need to remeasure with the next box. Best way to keep consistency is to use a bullet comparator and measure each bullet, and segregate them into seperate lots. Its a bit of time consuming labor, but if your looking for consistency, its the only way. I use a horady locknload comparator on a mitutoyo digital caliper that reads to .0005. I segregate by uniformity, not actual length (base to ogive).
 
Remove your seating stem and check it on the bullets you plan to reload.
I think theres still plenty of reloading seating dies made that have not updated there stems to fit more of the modern bullet profiles.
Many of us experienced this when the polymer tips started to show face.
 
Like stated for rifle stuff the stem should contact the ogive of the bullet. If you see any deformation of the tip probably need a different stem.

There are a lot of things that can affect your seating depth.

First how are you measuring seating depth. Hopefully your measuring to the ogive and not the tip of bullet. The ogive is going to be the only important measurement and is also going to be more consistent across bullets.

Some brands of bullets are very inconsistent bullet to bullet, this will have to be figured in to your tolerances.

Also your neck consistency will play a large role. Are you annealing, is brass squeaky clean? Without some type of lubricant be it carbon or something like graphite in the neck you will see a lot of variation as well.

When I’m working up a load I try to find a spot where small variances in BTO do not affect accuracy. You should be able to find a window where .005”-.010” difference won’t affect accuracy. Once I find something suitable I’ll load to close side of the window so as lands erode it’ll stay within that range. If I only have a window of couple thousandths I’ll usually keep working away from lands until it gets more forgiving.

TBH the last two barrels I pulled on my 6BrA were both around 2500 rounds and one I change seating depth once, the other I never touched the entire barrel.
 
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