O-ring under the lock ring ??

[bobinpa]

For those of you using an O-ring under the lock ring of your die: Why do you use it? I understand the concept of letting the die "float", but what purpose does the O-ring serve? I just got done sizing approx. 40 cases. 20 with the lock ring and O-ring and 20 with just the die loose in the press as an experiment. They all came out the same. In my opinion the O-ring and the lock ring serve no purpose for maintaining a dimension. The O-ring is only their to keep the die from moving so you don't lose your setting while allowing the die to float. What are you opinions?

 

[rogn]

OK

 

[Uncle Ed]

The o-ring allows the die to float and self center in the presses threads and not rotate.

Think of the floating die in the Co-Ax press.

 

[DirtySteve]

I use them...

 

[Sniper338]

I dont use em. Never saw a difference, and I like a locking ring so the setting stays set.

 

[bobinpa]

The o-ring allows the die to float and self center in the presses threads and not rotate.

Think of the floating die in the Co-Ax press.

I understand and agree with that....so what is the point of the O-ring other than to keep the die from rotating? In my opinion if your die doesn't rotate while you are sizing, the O-ring serves no purpose, correct?

 

[jepp2]

Why do you use it?

I started using it to see if it improved case neck TIR during sizing. I didn't see any positive benefit from the O-ring, but learned several other things that made improvement to reducing runout.

However, I fouind I liked the O-ring for holding the die in position and never moving, yet allowing easy very minor adjustment of the die without fighting the problems lock rings can cause. So I use them on all my sizing dies now. I can easily change case sizing length by less than 0.001" using the O-ring. I can't do that with just the lock ring.

Regarding your question about losing the die position. If I understand it correctly, I will frequently make minor adjustments to sizing length and the O-ring allows this. I just make a mark on the die and reference it off a point on the press reduction bushing. I might do this for different rifles, or brass that hasn't been annealed recently.

 

[watercam]

You are correct in that one does not need an O-ring to free float your die. It may be handy to not allow the die to free float to the point where it rotates one way or the other over the course of sizing/seating and thus compromising the precision of one's shoulder set back/bullet seating. The o-ring is there to hold the die in place so that your results are repeatable. If you want you can mark the die and press bodies to align your die in the press and simply keep an eye on the two while you size and seat several hundred rounds of ammunition. Or you can use a very inexpensive rubber retainer to do the hard work and allow one to load hundreds of rounds of match grade ammunition with some hope of precision so as to impress yourself or those with whom you compete. Your choice.
Every shade of impertinence is fully intended but offered as a humorous accolade of the precision reloading experience.
In other words, please accept my apology in advance and good shooting!
I will hate myself in the morning...

 

[watercam]

If this does not get me kicked off the forum, nothing will!

 

[DUSTY NOGGIN]

i dont understand what the oring thing is self centering , is it just a bandaid for a press axis square problem or just off perependicular shell holder , or an outta square press ram end/shell holder socket ??? since most presses are endless warrantied why not just fix the press , or shell holder

wouldn't bottomed out competition shell holder be a better squaring of the die to the shell holder . bottom it out then lock it down hard ??? doesnt really apply to the coax

can someone please explain how runout may be induced by sizing without a o-ring and where your find the bend/runout ?

 

[Dusty Stevens]

The o-ring started as a way to bump a couple more thou without loosening the lock ring on the die.... then along came somebody that figured it was for floating the die when the ram and slack in the shellholder is what did the floating. It has to help runout right? No- if it does its just a coincidence. You can put a die in a vise and hammer a case in or use a hydraulic wheel bearing press- the die does what its going to do as long as your press doesnt crazily push it in at an angle. Even the cheapest wore out lee press does the same thing as a rock chucker with the same die

 

[BoydAllen]

I have some pretty decent sizing equipment, and I can see some slight improvement in case straightness, measured at the case mouth, using a Sinclair concentricity gauge, comparing a regular lock ring with a Lee that has an O ring built in. That is all that I really need to know. If I had a lathe, I could make a jig to tell me if the sizing cavity of dies was coaxial with the threads, but I do not. So I do the simple comparison test and proceed accordingly. Another thing to ponder is whether the faces of lock rings are perpendicular to the CL of the threads. A friend and I did check this out on his lathe and I have a number of lock rings that have been trued. The most important issue here is whether any of this makes any difference at the target, and I have not been able to see that it has, probably because the differences are very small. I can tell you one thing, based on the earliest tests that I did, when I first got a concentricity gauge. Not all dies respond the same. I found that some did better locked up solidly, and some did better floating. The only way to tell was to test the die both ways. Do you have a gauge?

 

[cw308]

I use the O ring for the reasons as Dusty and a few others have stated , allows me to make minor adjustments without unlocking the lockring . Also make it easier to remove the die from the press . I tighten the die with the o ring ,the die doesn't feel loose on the press but still allowed the case to self center .

 

[DUSTY NOGGIN]

every time i use a gauge. i find runout is generally caused by brass variations at neck wall or expander pulling through crooked usually when neck is being worked hard between minimum od & then maximum ID. you can fix the neck and the amount you have to work the brass. is there a different cause of runout that maybe i haven't experienced,

wouldn't the slight side wall taper of a bottle neck case center it enough, you usually feel force of the sides being squeezed together well before the neck enters the sizing portion of the die - meaning wouldnt it have self centered already without the use of a o-ring ??

 

[R.Morehouse]

PMA Micro Die Adjuster works for the tweaks.............

 

[msinc]

.......Every shade of impertinence is fully intended but offered as a humorous accolade of the precision reloading experience....

I don't know what in the hell you is tryin' to say boy, but damn...it sure is purty!!!!! Next time I gets married I want you to be the preacher!!!
Seriously, that's good.....I like that. I just tried it on my wife and she slapped me......I gotta go now.

Edit: one hour later and I'm indebted to you sir!!!!!! She beat me senseless!!!

 

[natdscott]

The o-ring allows the die to float and self center in the presses threads and not rotate.

Think of the floating die in the Co-Ax press.

The die doesn't float in a Co-Ax press. It's just in a slot. When you cam the press shut, the die's TOP ring surface bears as solidly against the cast steel of the press body as any conventional press/die.

...and I dare you to try to get a normal O-ring to fit in there.

 

[Medic505]

The die doesn't float in a Co-Ax press. It's just in a slot. When you cam the press shut, the die's TOP ring surface bears as solidly against the cast steel of the press body as any conventional press/die.

...and I dare you to try to get a normal O-ring to fit in there.

Absolutely correct. The case "floats" in the shell holder, which some "reloaders" (ty Mr Guffy) have a problem with. If I could only invent a floating die/ shell holder/ case press that would size to a nats ass, I'd be a rich man.

 

[Uncle Ed]

The die doesn't float in a Co-Ax press. It's just in a slot. When you cam the press shut, the die's TOP ring surface bears as solidly against the cast steel of the press body as any conventional press/die.

...and I dare you to try to get a normal O-ring to fit in there.

The die in the Co-Ax press is free to move from side to side and self center and float in the press. Meaning the die is not confined in the press threads and self centers.

And in a standard press the die can be locked down off center and even tilted in the press threads. This is why you should not tighten the lock ring until a lubed case is inside the die at full ram extension. The Lee lock rings also have a rubber o-ring that allows the die to float and self center in the press threads.

O-Rings on Dies May Reduce Run-Out
https://www.accurateshooter.com/technical-articles/reloading/o-rings-on-dies-may-reduce-run-out/

 

[natdscott]

The die in the Co-Ax press is free to move from side to side and self center in the press.

It still doesn't float like an O-ring equipped die in a conventional press.

I've loaded north of 10,000 rounds on my Co-Ax...far from comprehensive experience, but it is more than none.