Lee collet die observation

[bow shot]

FWIW, this was my experienc working .204 Ruger brass...

I mentioned in another thread that if my brass had poor (say .004") TIR before or after sizing with the Lee Collet, that repeatedly bringing the brass back into the die while rotating the shell (AND holder) 360 degrees in small increments brought the TIR of the brass down to an acceptable level (.002" or less).

An update on that method: I found recently that just rotating the shell and holder ONCE, 180 degrees, was the superior method (most people recommend this). Neither method worked every time though.

Also, I found that if I backed the cap of the die out, and brought the brass back into the die repeatedly while screwing the cap to home, that this was more effective for reducing brass TIR. May be the same thing as backing the whole die out….

It needs to be known that this worked for me with quality brass (Nosler) having low neck wall thickness variation (0.001 – 0.0015”).

I’m sure that this is tough on the brass too, since it is being worked more...

[Unclenick]

Unusual. The one British publication that tried this found the collet die the only one to produce 0.001" runout or less. They probably used 180 degree rotation to clear the collet slit marks away.

It sounds like the mandrel may not be coaxial with your press ram? Try removing the locking nut and rolling the die on a flat surface while you look inside to see if the mandrel has wobble? If so, it is a candidate for replacement.

If not, try putting some grease on the die threads and using the die without tightening the nut or with only very light nut tightening that just lets its o-ring kiss the top of the press. That should let the die self-center a little. See if that makes cases better or worse? If that makes it worse, check that your shell holder is properly square across the top of your ram so that contact with the collet in the die doesn't force it off-axis? If it is does, try the opposite strategy, reversing the locking nut in the collet die to get the rubber out of contact with the press and tightening it enough with a wrench so the ram contact can't tip it.

[woods]

The Lee Collet has a free floating mandrel even if the cap is screwed down tight. To test this, thread the die into the press, reach up under the die and you can wobble the mandrel around with your fingers. That is what makes it possible to reduce runout since your case is concentric when it comes out of your chamber from firing.

I use a lot of Lee Collets/Redding Body Dies, love 'em.

[bow shot]

Yeah, I realize this is kind of wacky. And at this stage, I'm not confident that it is an "it works all the time" thing at all.

As I free up brass, I'll be giving attention to the points y'all mentioned.

[Unclenick]

It's been awhile since I last took one apart and forgot how much wiggle room the mandrel has in its bushing. Not fully free floating, but significant play. I pulled my .223 Collet die out and tried rolling it over a surface plate a few times. The tip still appears pretty steady if I don't go too fast as the mandrel flops into place. However, popping the retaining cap and pulling the mandrel half way through the bushing so its balance point is supported in the bushing will let you roll it to see if either the bushing or the mandrel are wobbling (bad bushing or bent mandrel). You can remove the mandrel and roll it on a flat surface with the small rim at the top overhanging the flat surface. That will verify neither the mandrel nor the decapping pin is bent. You can remove the bushing and pull the collet out of the top to roll it on a flat to check that it wasn't machined off-center? (if you don't have a surface plate, a small square of plate glass makes a good flat surface.)

A couple of additional thoughts occur to me: The decapping pin on the mandrel is guided into the flash hole in the case, which is why having it bent can throw centering off. Double-check the brass for off-center flash holes. That's not so likely in the Nosler brass, but is an issue with Lake City and some other mil surp brass, and that would pull the mandrel off the case axis. Another is to disassemble the die and make sure no dirt or debris has got between the mandrel and bushing or the bushing and the die body or the collet and the die body, any one of which might pull the case out of square with the collet jaws or the shell holder. You could add a pin head's worth of grease to the top of the mandrel to make sure it slips against the cap when decapping is pushing it up.

Loosening the die cap is not the same as raising the whole die, as the latter raises the collet closing starting point, where the former does not. I suspect you are just improving how much the mandrel is free to wiggle into center when you do this. Since you are only talking a couple of thousandths, you could actually ream the hole through the mandrel's bushing slightly bigger to encourage this self centering.

[bow shot]

As always, good avice, folks, thanks kindly!