AR Colleagues,

I would like to hear opinion and experiences on how you install the decapping rod/sizing button on your resizing dies.

Here is my routine procedure: I use Redding die sets primarily. My normal procedure is to adjust the sizing die (with decapping stem removed) to PFLR on a fired case with slight resistance to bolt closing to ensure minimal sizing in that chamber. Once the die body is set, I install the decapping stem. Generally I purchase and install the carbide size buttons offered by Redding which I note are free floating on the stem. The stem is installed in the die body to allow the decap pin to protrude below the base of the die a sufficient amount to allow full primer removal. I then choose a fired case that shows minimal runout and run it into the die enough to just allow the sizer button to enter the case and center the stem within the die body. The lock rings are then tightened down and I will resize a few lubed cases and check for runout. Sometimes I will slightly readjust the decap stem if run out is high but since the size button is self centering I never found it to make a lot of difference.

A recent article in Precision Shooing by Mic McPherson talked about installing a small “O†ring between the top of the die body and the bottom of the stem lock nut to allow the decapping stem some flexibility and to “self center†on the case. He also talked about using a similar setup on the die lock ring against the top of the press to allow the whole die to center on the case which is apparently the method used by Lee products. It all seems to make sense to me but I wonder if one would have to worry about “creep†and I would think the repeatability factor might be an issue each time you remove and install a die.

I would be interested in other reloader’s techniques that they use to minimize runout and load accurate ammunition when setting up sizing dies.

Thanks
Paul

Sounds good to me. I use mic's "o" ring thing too. No creeps, except in lefty democrat circles.

On my serious long range rifles (especially with custom chambers) I decap on a universal decapping die with no sizing button and then I size with a Redding S type bushing die. I don't like pulling the sizing button through the case neck with it unsupported, it tends to pull the neck forward.

Using the carbide sizing button, you have already floated the process and there is no need to float the stem with an O-ring.

I would measure my case run-out before getting too upset over putting an O-ring under the die-lock ring. It's easy enough to experiment here, but you may want to assure yourself that you're actually accomplishing something. If you have a good press and dies, there may not be much to gain. The thread/die connection in my press is so tight that an O-ring won't introduce compliance, but it will serve to allow the die to loosen occasionally. If there's no inherent misalignment in your press/die assembly, introducing compliance won't accomplish anything.

The shell holder allows some compliance, but there are those who advocate replacing the spring clip retainer with an O-ring. Use your run-out gauge to determine if there is any benefit.

As has been mentioned, most find benefit in using a bushing sizer and eliminating the sizing button.

About a year ago I was asked by Hot Core in a private message to try the o-ring thing and check for concentricity since I have a concentricity "thingy" and he doesn't. We engaged the help of another reloader, bounty hunter, since I didn't have the time right then.

bounty hunter did some tests using the o-ring with the Redding sliding expander ball and compared it to the Lee Collet Neck Sizer. I do not still have the results but I do remember that the o-ring did not show any significant reduction in runout. The Lee Collet showed significantly lower runout in identical cases sized at the same time by both types of dies.

After you install a Lee Collet Neck Sizer in the press you can reach up under and move the decapping/sizing mandrel around by hand even though the die is tight. This means that the mandrel does not exert any sideways force on the case neck as the collet is tightened to resize the neck. It produces very little runout and is inexpensive also.