Using an O-ring on the resizing die – what is your experience?

[STS]

I have used a method for the last several years that seems to work well for me. I don't use either a lock ring or o ring. I have a witness mark on my press and simply use a small lump of clay to keep the die from rotating in the press. The clay rests on top of the press and contacts the die threads. It works to perfection and allows me to make small adjustments if needed effortlessly. Sounds a little odd, but if you will give it a try I think you will find that it is an excellent method to get the results you are looking for.

 

[jo191145]

I use O rings on my FL dies that use an expander plug. I place the O ring between the die body and lock ring on the decapping rod. This allows the expander to float as it is being drawn though the neck. This has reduced runout.

As I understand it (could be wrong) the method you described is the original O ring fix for run out with sizing dies that use expanders.
I do my best to get rid of expanders but in the few cartridges I load for that still use them thats where the O Ring goes.

FWIW If anyone has standard seating dies an O ring between die body and seating plug lock nut is also a wonderful thing.
It really makes seating depth adjustments smooth as you never need to unlock and relock the nut, just turn the screw/knob.

 

[FroggyOne2]

If you like the Lee style of die locking rings, I can put a set screw in it for you.. Just pm me about it.

 

[savageshooter86]

does the O ring under the die body and between the press help with seating dies and body dies? Or mainly just FL sizing dies

 

[amlevin]

does the O ring under the die body and between the press help with seating dies and body dies? Or mainly just FL sizing dies

Any die that needs to line up with the case "axis".

 

[bsekf]

I use both the o-ring and just leaving the die loose in the press. I would think using a set screw in the lock ring might cause the die to tip in the lock ring due to slop in the threads. Wouldn't make much difference on the up or sizing stroke but it would effect the down or expander stroke. I use a sharpie to make witness marks, they wipe right off with a little WD40.

 

[BoydAllen]

Years ago, I did what I thought was the ultimate floating die test. I fitted an old die lock ring, the kind with a set screw, with a long screw that would extend perhaps an inch from the outside of the ring. Then I made up a piece that I could secure in the slot in the top of the press, that takes the primer tube holder, that had a U of heavy wire brazed to one end, that was designed to trap the extended set screw so that it was free to move up and down, but the lock ring could not rotate. With this setup, the ring was locked on the die above the top of the press (a Rockchucker), so that the die was truly floating, and only restrained from rotating. I tried several different one piece FL and neck dies that I had, with this apparatus, comparing the runout of brass with the dies floating, and with them locked solidly down. In some cases the floating die did better, and in others the result was better locked down. I realize that this test was far from scientific, but, given the topic under discussion, I thought that some might find it interesting. With a little work, it would be easy to duplicate.

 

[FroggyOne2]

BSE,

I personally do not use a expander ball in the sizing die. Instead, I use a expanding mandrel. As soon as I get set up for it, I will be making custom sized mandrels to suit my needs. I use a K&M mandrel holder.

 

[K22]

As stated by some other posters, I've also use the "o" ring between the expander stem and body of the die. I've notice some improvement in run out, especially with my 308, but have not seen any significant difference in group sizes. Both with and without the "O" ring the groups average about .600 moa at 100 yards. Still, I continue to use the "O" ring under the stem - I like the idea of less run out even though I have haven't seen the results in my groups.

I don't like the idea of placing the "O" ring under the body of the sizing die because of concern of potential die rotation and thus interferring with achieving a consistant shoulder bump which is critically important to me.

 

[BoydAllen]

I can tell you for sure that your concern is unwarranted. The threads are what keep the die from moving upward in the press, not the lock ring. It keeps the die from rotating in the threads, and since all of the force imparted to the die during sizing and expanding (if you are using an expander ball) is up and down, it only takes a small amount of friction to hold a die's setting in the press. I use a Lee lock ring on my 6PPC's FL die, and no one is more picky about shoulder bump than I am for that application. I set up the die for each batch of brass, to take in account batch to batch differences in work hardening, and monitor my results after setup, to make sure that I am getting what I want. My bump settings are in the range of .001 or less, and the results that I get are very good.

 

[K22]

I can tell you for sure that your concern is unwarranted. The threads are what keep the die from moving upward in the press, not the lock ring. It keeps the die from rotating in the threads, and since all of the force imparted to the die during sizing and expanding (if you are using an expander ball) is up and down, it only takes a small amount of friction to hold a die's setting in the press. I use a Lee lock ring on my 6PPC's FL die, and no one is more picky about shoulder bump than I am for that application. I set up the die for each batch of brass, to take in account batch to batch differences in work hardening, and monitor my results after setup, to make sure that I am getting what I want. My bump settings are in the range of .001 or less, and the results that I get are very good.

Thanks for the advice - perhaps I'll give it a try - the "O" ring under the body of the die and see if I can achieve some improvement. I have an additional problem with my run out gage - like me - it's an old (RCBS) and it's difficult to get precise run out measurements but it's sufficient enough that I was able to detect improvement with the "O" ring under the expander stem so I'll try it under the body of the die. Always looking to get better.

 

[FroggyOne2]

Boyd is correct in what he is saying.

 

[Tom Bear]

In answer to the original question, if this is the method under discussion http://riflemansjournal.blogspot.com/2009/08/reloading-headspace.html, then yes, it is an outstanding way to use a FL die (in my case RCBS) and bump case shoulders back only 1 to 2 thousands. Great discussion here, also.