Floating Dies?

[Bullydog]

Does anyone here have any experience with the effects of floating your dies,ala Forster Co-Ax)? I have a Dillon 550 that I use for most of my ammo, from 45ACP up to 300WM. I'm thinking of floating the some dies the way David Tubb describes in "The Rifle Shooter". However I've been thinking about the concept behind floating dies, and I can't wrap my head around how it makes better ammo.

It seems to me that when the case first makes contact with the bottom of the die, it will push the die up, effectively locking it against the top of the theads. The die is no longer free floated, it's now "hard-mounted". The only difference is that it's hard mounted to the top of the press threads instead of the bottom. The 1/10,000,?) or so of an inch free play doesn't seem like it will help much. I know that people talk about how floating dies center on the cartridge more, but considering that the case is free to move around on the shellholder, I don't know how much of an improvement it can be.

I'd like to see if anyone has any positive or negative experience with floating dies before I swiss cheese my expensive die heads and lock rings. I'm looking for "hard" facts like better concentricity or improved groups.

Thanks.

 

[acloco]

I use a Forster CoAx. Yes, the coencentricity is down to 0.0002".

I have not seen Tubb's info on floating a 550.

But, know this. The end result is how the axis of the press, shell holder, AND dies end up.

If two of the three float, you should be just fine.

 

[robbor]

What is the TUBB method?
I have heard of using an o-ring under the die lock ring and tightening the die against the ram but I just made concentricity gauge this year and have yet to do any loading and test.

 

[Bullydog]

I use a Forster CoAx. Yes, the coencentricity is down to 0.0002".

Do you happen to have the runout readings for those same dies on a non-floating press?

 

[Bullydog]

What is the TUBB method?
I have heard of using an o-ring under the die lock ring and tightening the die against the ram but I just made concentricity gauge this year and have yet to do any loading and test.

Basically you drill a small hole into the die head near the threads. Into this hole you insert a roll pin so that it sticks straight up, like a post. Then take a large diameter lock ring such as those made by Forster, and drill a hole into the flat part that is slightly larger than the roll pin. When you go to mount the die, slip the lock ring over the roll pin, hold it slightly above the head, and thread the die through both the lock ring and the head.

 

[Rustystud]

Bullydog:
First, If you load on a Dillon loader as a turrent loader instead of as a progressive there is enough slop in the tool head and shell plate to allow your case to float. That changes when you start using more than one die simultaniously.

Are you familiar with how the Manson floating reamer holder works? It uses a tool holder that mounts into the tailstock that has a surface ground surface with three shoulder bolts set at 120 degrees of each other. The tool holding end is also has a surface ground side that is machined so the shoulder bolts hold the two surface ground sides together. The two parts can be pushed by the tailstock toward the headstock. But they can float concentrircally to each other. This can be duplicated by taking shell holders for a single stage press and machining the bottom flat and making a shell plate for your Dillon. In essence you would be making 4 independent floating shell holders. I have talked to Kent Reeve, and John Widden about this idea.

Rustystud

 

[Winchester69]

Has anyone found any measurable benefit to using, in a standard single-stage press, a loose-fitting shell holder to effectively float the brass?

 

[Bullydog]

Rustystud-

I don't think I'm following you,I've never seen a Manson reamer holder before). From what I understand, you would basically mill standard shellholders down so they essentially look like a Lee autoprime shellholder,flat on the bottom). You then place these in a modified Dillon shellplate. The cases are then slid into the milled shellholders instead of slipped between the ram and the shellplate.

Is that the process you're describing? If so I'm confused as to the advantage provided by the modified shellholders over a standard Dillon shell plate. My shellplates are loose enough that the cases are free to rotate about the x and y axis, as well as slide horizontally.

Can you explain this a little more?

 

[Rustystud]

The shell holder would float inside three shoulder bolts set up as piillars with the socket cap head holding them from coming up off the shell plate. Look up the clymer or Manason floating reamer holder. Then immagine milling of the base of a RCBS shell holder flat. Mill slots at 120 degrees apart through the shell holder just larger thean the shoulder bolts bodies but noth their heads. The shoulder bolt heads will be below the surface of the shell holder. Then mill a step in the top at the same points where the slots are for the top of the shoulder bolts to ride back in forth but holding the modified shell holder down on the shell plate. The modified shell holder will be able to float concentrically for about .0040 but remain fixed to the shell plate. When the case is inserted into the modified shell holder and run up into the die the shellholder will self align within the float of the shell holder thus perfectly aligned dies in a progressive press.


Rustystud