best method to adjust seating depth.

[BJung]

I use a Rockchucker to reload with and am making testload based on different seating depths. I have a dummy load where the bullet ogive just touches the rifling and am seating the depth in increments. If I seat the bullet and get the correct COAL and tighten my die down, the seating is not always consistent. And so, I'll seat my bullets close to desired COAL and turn my seating die down in increments and measure the COAL. I would turn the seating stem down, measure.. nothing, turn it down more.. nothing.. a little more.. and the bullet seats too deep? Can I use a collet puller to pull the bullet back out and reseat it again. Can I make a sleeve like a cut tube that touches the ogive and the seating stem?

 

[dcloco]

Your rifle seating die should seat every bullet to the consistency of the ogive length of each bullet out of the box.

IF you are using VLD or plastic tipped type of bullets, more than likely, your seating die stem is not machined to handle this type of bullet correctly.

With a sharpie, blacken the upper 1/3 of the bullet and seat. Truth will be told at this point..

 

[Okie_Poke]

A bit more information may allow folks to help you a bit better: (i) for what are you reloading, (ii) what bullets are you using, (iii) what seating die are you using, and (iv) in what increments are you trying to adjust?

Here are a few thoughts from me without knowing more details. I'm assuming you're reloading for a rifle because that's what I know best.

• For every seating die I've ever used, I adjust the seating depth using the seating stem and not by turning the die down.
• When I use a dummy load to reset my seating die, I sometimes have to adjust it down a few extra thousandths of an inch in order to match the same seating as the dummy round. This is particularly true if you're using compressed powder charges.
• A lot of bullets, particularly hunting bullets, vary more in length than one might expect and therefore loaded ammo may vary more in COAL than one might expect. Measuring from cartridge base to ogive (CBTO) with a comparator rather than just measuring the COAL often shows less variation. If the CBTO is consistent, they will probably shoot consistently.
• As dcloco mentioned, it's possible your seating stem is not shaped appropriately for the bullet you are using and that can cause inconsistent seating depth. You can check this by removing the seating stem and putting it over the nose of a few of your bullets and seeing where it's contacting the bullet and how consistently. If the tip is bottoming out in the stem before the stem contacts the ogive, that could be it.
• Due to the potential for variation from bullet to bullet, I will often try seat several bullets at the same die setting and measure them all before I decide whether I need to adjust the die or not. Again, a lot of bullets aren't as consistent as one might expect them to be. If you're using factory second, fmjs, or non-premium bullets, it tends to be worse.
• Unless you're using top-shelf components and reloading equipment, my suggestion is to not get too hung up on a variance in a few thousandths of an inch in seating depth. It's probably a fool's errand to try to eliminate the variance entirely if you're using hunting bullets or non-premium bullets, and they'll probably shoot just fine unless you're trying to make little bitty groups at really long range (in which case you need premium components and tools and advice from someone other than me).

 

[Varminterror]

I'll seat my bullets close to desired COAL and turn my seating die down in increments and measure the COAL. I would turn the seating stem down, measure.. nothing, turn it down more.. nothing.. a little more.. and the bullet seats too deep?

This is happening because of stiction. The pre-seated bullet isn’t moving in the case neck until the displacement becomes far enough to allow enough force to make the bullet slip in the neck again. Until then, you’re just flexing the die, brass, and press, and not overcoming the neck tension.

If you’d seat another bullet, instead of reseating the same bullet, the position would have changed with the first adjustment.

Can I use a collet puller to pull the bullet back out and reseat it again.

I don’t like using a collet puller for this, as it has to squeeze the bullet, maybe influencing the jacket to do so. Inertial puller will cause less bullet influence.

Equally, there’s always consideration that a bullet which has been seated is different from a bullet which has not. It’ll seat slightly differently, and may even shoot differently.

Additionally - @jmorris may be along soon to offer a photo of his dial indicator jig he made for non-micrometer seating stems, but the depth gauge on any vernier calipers can be used to do the same. When you find your land-kiss length, note the COAL of that bullet, pick your desired jump, then use the caliper depth spindle to measure the height of the seating stem, zero the caliper, then reduce the length down to your targeted jump.

Finally, if your stem doesn’t fit your bullets, fix it or replace it, or both. For example, if you are shooting VLD’s/ELD’s with sharp points and long radius count ogives, drill a recessed mortise into the center to clear the tips to make sure you are only making contact with the ogive. If you’re getting limited contact between the ogive and seating plug, even with a ELD/VLD stem, obvious by leaving a ring on the ogive (or worse, collapsing/deforming the nose), then either lap or bed the plug to better fit the bullet profile.

Two questions, however: 1) How much neck tension do you have? And 2) how are you cleaning your brass and 2.1) if you’re using any wet cleaning method, are you lubing your necks? Or 2.2) if you aren’t cleaning, are you brushing your necks?

 

[tightgroup tiger]

This is happening because of stiction. The pre-seated bullet isn’t moving in the case neck until the displacement becomes far enough to allow enough force to make the bullet slip in the neck again. Until then, you’re just flexing the die, brass, and press, and not overcoming the neck tension.

If you’d seat another bullet, instead of reseating the same bullet, the position would have changed with the first adjustment.

That is spot on.
The case itself is giving enough that the bullet doesn't move until you change depth enough to overcome the friction (stiction). Stiction is a valid term we use in engineering.

 

[rfwobbly]

I've found that a lot of OAL inconsistency is simply being a novice reloader. You did not say how long you've been reloading, but concentrating on the op handle movement is critically important. It's sort of like pulling a trigger... an art that needs to be practiced in slow motion until the brain gains the "muscle memory".

Just focus on being slow and consistent with the motion of the op handle.

 

[AJC1]

I've found that a lot of OAL inconsistency is simply being a novice reloader. You did not say how long you've been reloading, but concentrating on the op handle movement is critically important. It's sort of like pulling a trigger... an art that needs to be practiced in slow motion until the brain gains the "muscle memory".

Just focus on being slow and consistent with the motion of the op handle.

That's the same description I gave junior two days ago when he got .010 variation when I was getting .005. The same can be said about the amount of torque applied to a fastener if you spin wrenches. My dad used to joke about it a lot. Tighten a bolt and say that's about 40 ft lbs. Feel is a thing that is very valid at the bench from primer pockets to sizing cases but it's entertaining listening to us try and describe the "feel".

 

[Ru4real]

The time to begin COAL adjustments is when your load and gun combination is already MOA or sub MOA. I assume you are there?

I also use a Rockchucker. In the process of locking the die down, I usually end up with 3 or 4 loaded rounds before it’s where I want it. Those rounds are used for shooting boulders

Twenty five years ago I wasted a lot of time playing around with every loading variable, COAL included, to try make a particular rifle shoot really well, resulting in marginal gains. Today that same rifle shoots just about everything well. What changed? That M70 hunting rifle now has a Krieger barrel.

 

[jmorris]

Additionally - @jmorris may be along soon to offer a photo of his dial indicator jig he made for non-micrometer seating stems, but the depth gauge on any vernier calipers can be used to do the same.

It’s just 3 blocks of aluminum that straddle the die and allow an indicator to be mounted above the die.



There are also some fairly cheap height gauges that would do the same thing. Just not as useful for other stuff in the reloading room as the indicator.

https://www.amazon.com/iGAGING-DIGI...saw+blade+height+gauge&qid=1673016734&sr=8-18

 

[film495]

no expert, but the OAL variation is largely from my limited experience some variation in the bullet ogive shape, and the way the seating stem contacts it to seat it. there are ways to tune that, but I've never bothered.

 

[jmorris]

”measure the COAL.”

That’s probably your issue.

Take just the bullets and measure them like this.

If they are different like these SMK’s OAL isn’t a measurement you should be interested in. Because the tip is inconsistent.

If you move back along the ogive you will find the measurements are consistent and that’s the part that can contact the rifling anyway.

If you don’t have anything you can drill a hole in and don’t want to buy another tool, you can remove your seating stem and measure it along with your loaded rounds, as this will also eliminate tip variation from the equation.

 

[Varminterror]

I’m no expert either, but damned well versed in measuring various bullets.

The most common culprit in COAL variability with rifle bullets is point variability. Our seaters don’t contact the points, the meplats, they contact somewhere down the ogive, so even when the ogives are exceptionally consistent, the meplats may not be, by several thousandths. It’s pretty rare to find bullets with several thousandths variability in the bearing surface position or in the ogive, but the slack material remaining at the meplats can vary wildly.

 

[JFrank]

I would not measure coal other than to sort bullets or set the seater to produce mag length ammo as oal effects BC of the projectile.
My source for this is Bart sauter ( Barts bullets ) and Tom Jacobs ( Vapor Trails)
Once I had variations in seating depth that traced back to the die being out of adjustment another time the seating stem was making contact with meplats.

 

[Okie_Poke]

This is happening because of stiction. The pre-seated bullet isn’t moving in the case neck until the displacement becomes far enough to allow enough force to make the bullet slip in the neck again. Until then, you’re just flexing the die, brass, and press, and not overcoming the neck tension.

If you’d seat another bullet, instead of reseating the same bullet, the position would have changed with the first adjustment.

I didn't know there was a name for this, but this makes perfect sense and is consistent with what I've observed over the years. I always seat and measure a few more after I think I'm done adjusting the die to make sure it's seating the bullets where I want in one stroke. In my head I called it "confirming with a fresh bullet." I didn't previously know why I needed to do that, but now I do.

 

[film495]

that's a good tip, that for a quick compare to measure with the seating stem. I'm sure there's an modestly expensive tool to use for that, but the seating stem is a solid idea for those of us without all the do dads. i have so many do dads, I can barely keep track of them already.ll lol