Cases/bullets scraping in dies

[justpete]

Using a Co-Ax press,new) and a Forster 308 NM FLS die, properly adjusted, new Winchester brass is getting scraped along part of the back of the case to the bottom of the die travel. Using Imperial Die Wax and the dies are factory polished - amount of die wax doesn't have an effect.

Same thing's happening to 175gr SMKs in both a standard Forster seater and a Redding Competition seater. The former I polished about a mil out of the throat diameter,now about 0.3101") until the scraping occurs only about one in twenty rounds or so, if I'm careful using the press.

I haven't run enough rounds through the Redding die to have an estimate of the rate at which it occurs but so far it seems to be not significantly different.

The scraping looks like burnishing to the naked eye but under magnification,loupe) and the right light the many fine longitudinal scratches that make up the burnished area are visible. On the bullets they occur only on the bearing surface forward of the case mouth and only over a relatively small portion of the circumference. Rotation of the dies in the press doesn't change the location of the scraping.

If anyone can tell me if this is something to expect or not, I'd appreciate it. I'm new to reloading so maybe I'm just chasing a ghost. BTW, the runout of the loaded rounds and sized cases is quite good at about one to two mils and about a half a mil, TIR, respectively.

I've seen the same bullet issue with new Lapua brass but it was only neck sized so there's no scraping of the cases. And the runout of the bullets and cases was as good or better.

TIA, Pete

 

[Travelor]

It sounds as if the dies are not correctly aligned with the case. Ar you using the Redding brand Co-Ax lock rings?

The reason I ask is that it sounds as if your does are not "floating" like they are supposed to with the Co-Ax press

 

[justpete]

It does seem that way, yes.

I'm using Forster Co-As lock rings on all dies. The adjustment on the press that applies downward pressure on the lock ring through a spring loaded ball hasn't been changed and the dies do move vertically under action of the press as they should.

I haven't locked the rings with the press at the top of its stroke as it's kind of difficult to do. With ball-end hex drivers it might be possible, I'll give that a try.

The caliber-adjust screw which preloads the shellholder jaws open seems to make a bit of difference in that the shell is more free to move laterally but there has to be a force applied by misalignment for this to happen. If this force is applied by a sharp edge in the die where diameters change a bullet would be scraped since the case isn't going to move without friction.

But if this step were radiused, where the die steps down from an ID to clear the case neck to the tight tolerance throat the bullet seater slides in for example, damage to the bullet surface would likely be less or even non-existent. I can't think of a way to make this change to either the Forster or Redding die interior profile.

This doesn't address the case scratching during full sizing though at least not directly although radiusing the entry ID of the die might help. That's something I can try to do along with more polishing.

BTW, the 'damage' to the bullets happens every time with the Redding die but not very often with the Forster die, now that I've used it enough. The 'damage' is minimal but it's there and it just doesn't seem like this would be normal.

 

[justpete]

Edited to say I clearly didn't understand how this type of seater die works. The bullet is already as far into the seating throat as it will go as soon as the case is fully inserted. The only thing I can figure is the scraping is happening after seating when withdrawn. I give up...
===============
Correction: The new Lapua cases are scratched from being run through a factory polished 308 NS die. I did manage to forget to deburr them so it's no surprise, I think. The die shows numerous longitudinal scratches in the case body and neck areas.

Some Nev'rDull cleaned it up a bit in both the NS and FLS dies but I applied some KG12 to remove any brass buildup that may look like a scratch in the neck area although it didn't do much with fifteen minutes soak.

And checking the bullet seater dies again:

Running a bullet and case into either die by hand without compressing it shows no scratches, scuffs, or burnished areas of any kind.

Seating a bullet by either of two methods 1) set case on shellholder bearing surface with bullet set in case mouth and run through the die or 2) insert case and loose bullet into die by hand and raise shellholder until jaws cam over the case rim and then compress the die to seat the bullet shows no difference in 'damage' characteristics or frequency.

Adjusting the shellholder jaw assembly has a minimal effect. Tightening the assembly screws snug but not overly tight, as suggested in the manual which I missed the first time, has no significant effect.

After seating and verifying 'damage' placing the seated round back in the press and running it back through either die does not further damage the bullet even if run through repeatedly.

So running the case and bullet into the die without compressing it doesn't seem to be the cause and neither does absolute alignment.

The damage isn't evident on the bullet surface that's inside the case mouth, only on the bearing surface ahead of it.

Raising the shellholder enough to compress the die and push the bullet into the seating throat far enough to allow contact of the bullet's bearing surface with the ID step must be the cause. And the 'damage' would be complete before the bullet is seated by the rest of the movement of the case.

It's impossible for the OD of the bullet as located by the case neck and its chamfer to be perfectly aligned with the throat before the compression starts. That the 'damage' to the bullet decreased as the Forster die was honed out a few tenths at a time tends to support this view, I think.

Once the bullet is seated the previous, unseated error in location of the bullet OD is removed keeping the bullet from contacting the seating throat when running the seated round back through the die, which jibes with what's happening.

From this I'm assuming this must be normal or I'm missing something really obvious here.

Thanks for reading this far. I'm off to the click the donate button. Pete