Reloading Dies & O-rings

[Bart B.]

Are O-rings needed to install reloading dies properly in presses?

Why don't dies making cases and bullets use them?

[Unclenick]

I remember John Feamster writing in Precision Shooting about using an O-ring under the die lock ring in an attempt to get the die to float a little for self-centering to try to reduce concentricity errors in the finished ammo. I played with it some, but never saw consistent benefit, though I never really did a proper statistical analysis of the results, either. Nothing outstanding happened is all I can say, so I vote 'no'.

[higgite]

1. No

2. Because they don't need to?

[olduser]

I thought this was just a Lee thing.

[akinswi]

check out this article

https://www.accurateshooter.com/tech...educe-run-out/

[FrankenMauser]

Are they needed?
No.

Are they beneficial?
Only if your press (or die) is out of alignment.

[BillyBoy 57]

I am going to follow this thread as I have Questions on the O ring myself ?

[LeverGunFan]

Our 7/8-14 reloading dies are solely located in the reloading press by the the threads on the die and the threads in the press. It is difficult to measure the runout of the die threads to the axis of the die, or to measure the runout of the press threads to the top surface of the press. So the die and press manufacturers rely on best machining practices to keep tolerances within reasonable limits, but there will be some misalignment due to the necessary clearance between the external threads of the die and the internal threads in the press. Will an o-ring help? Maybe, maybe not.

I'd expect that commercial dies do not rely on just the threads for alignment, they probably use a pilot diameter that can be held in close alignment to the axis of die and/or a shoulder that can be held perpendicular to the die axis. The best approach would be to not use threaded dies, but to use a clamping arrangement to hold the die in the press.

[Bart B.]

Originally Posted by LeverGunFan

Our 7/8-14 reloading dies are solely located in the reloading press by the the threads on the die and the threads in the press. It is difficult to measure the runout of the die threads to the axis of the die, or to measure the runout of the press threads to the top surface of the press. So the die and press manufacturers rely on best machining practices to keep tolerances within reasonable limits, but there will be some misalignment due to the necessary clearance between the external threads of the die and the internal threads in the press. Will an o-ring help? Maybe, maybe not.

I'd expect that commercial dies do not rely on just the threads for alignment, they probably use a pilot diameter that can be held in close alignment to the axis of die and/or a shoulder that can be held perpendicular to the die axis. The best approach would be to not use threaded dies, but to use a clamping arrangement to hold the die in the press.

Would that also apply to dies making bullets and cases?

[LeverGunFan]

Originally Posted by Bart B.

Would that also apply to dies making bullets and cases?

I'd guess that commercial bullet and cartridge equipment is much different than our typical reloading dies. Probably they would have dedicated multi-station die plates for each cartridge, with the cartridge or bullet form machined precisely in the plate. I need to find a company giving tours of their manufacturing facility.

[Metal god]

The rings only help on the down stroke . There is to much of a load on the die/threads when sizing a case for any little O-ring to make a difference. I learned this long ago with my Hornady bushing system. The nature of the design makes all dies in it free floating on a O-ring because thats how the bushing sits and stay’s in place in the press . The O-ring forces the bushing to make firm contact with the press as if there is already a slight load being exerted. This results in zero movement in the bushing on the upstroke . However on the down stroke the bushing and die can be seen moving quite a bit . It has very little to no effect on concentricity unless it can help center the expander button as its pull through the neck .

I have a concentricity gauge and I’ve seen zero positive effect knowing my dies are semi free floating .

[zeke]

Some believe in self centering, some don't. If your expander button is not "fixed in place" aka "free floating", it will self center to a degree in the previously sized neck.

Not sure how comparing that to a manufacturing process actually matters?

And there are numerous differing dies/presses/arrangements on the market that work differently. Am using a RC, and self center every sizing die used on it. Learned this the hard way with a Redding carbide 45 acp die where the sizing ring was slightly off center.

edited to add am used self centering incorrectly for setting up the sizing die, it is really squaring the inside cut of the die to the upward vertical force of the ram. kinda similiar

[Bart B.]

For what it's worth, best accuracy happens when the expander ball is removed and the full length sizing die neck is honed out to about .002" less than a loaded round's neck diameter. The die is set in the press to set the shoulder back a couple thousandths.

Sierra Bullets pioneered this in the 1960's.

[Bart B.]

Originally Posted by LeverGunFan

I'd guess that commercial bullet and cartridge equipment is much different than our typical reloading dies. Probably they would have dedicated multi-station die plates for each cartridge, with the cartridge or bullet form machined precisely in the plate. I need to find a company giving tours of their manufacturing facility.

Sierra, Starline, Hornady and Lake City Arsenal give tours of their facilities.

Note the way they test their stuff isn't much different than how we test ours. Automated machines make their process much faster. And the human variables are eliminated. Sierra's 30 caliber HPMK rifle bullets have to shoot inside half an inch at 200 yards.

[mehavey]

I need to find a company giving tours of their manufacturing facility.

Check-6 right here on TFL:
https://thefiringline.com/forums/sho...34&postcount=1

[rc]

O rings on dies are garbage. The best dies are RCBS but the best lock rings are Hornady in my opnion. Those split rings with the flats work much better than the allen screws into the threads RCBS now uses.

[zeke]

Originally Posted by Bart B.

For what it's worth, best accuracy happens when the expander ball is removed and the full length sizing die neck is honed out to about .002" less than a loaded round's neck diameter. The die is set in the press to set the shoulder back a couple thousandths.

Sierra Bullets pioneered this in the 1960's.

For what it's worth, certainly agree with that concept. None of my accuracy loads use an expander ball, have more interference fit than most find acceptable and use Redding comp seater if available. However was responding to another post about self centering the expander ball.

[Unclenick]

Rc,

Those are called cross-bolt lock rings. Forster has them, too.

[BillyBoy 57]

I will be looking these up , thanks !

[Unclenick]

Forster has a neat one now with graduations to help you adjust die height in thousandths if you want to pay the extra for it, but they also make plain aluminum ones. Here's the Lyman cross-bolt lock ring. This outfit is a new entry.

[HiBC]

As far as what works, it will be on the target and maybe the concentricity gauge.
I don't know what the criteria are for dimensioning and tolerancing a die set.

The dies and the press interconnect via the threads(exception,somewhat,the "Co-Ax presses) As they are 60deg Vee threads, ideally the male and female pitch diameters would mesh in a co-axial fashion. Think of it as a helical 60 degree Vee block. I suspect hose two threadforms(male and female) use the pitch diameters as datums and tolerance size.squareness,coaxiality,etc from there. Depending on the manufacturer,some form of mandrel gauging likely takes place. Almost certainly at Redding, Who knows at Frankford.

We can have trouble when a "renegade" unauthorized datum steps in. What does that mean? A lock ring drawing down on the top of the press might not be perfectly square with the die body. Especially if its jammed to one side by a setscrew.

An out of square lock ring Might disrupt the male and female pitch diameters from "finding" each other.

The crossbolt lock ring will be superior to the setscrew lock ring that way.

The Forster/Bonanza press does not place the press 7/8-14 threads in a menage a trois with the die body and lock ring threads.

Its my opinion that whether or not an O-ring is beneficial??? You'd have to know what you were trying to accomplish, use a consistent technique,and test results.

With quality die and press components, there may not be a problem to solve,

A lock ring with runout might work like an out of square Garand bolt face ,

Folks figure out workarounds. Maybe an O-ring is a workaround for out of square set screw lock rings. The O-ring would let the thread pitch be "in charge" I don't know! Folks are trying.

Over time,some gun/reloading work has been done on a gang drill (multi station drill press) and some gets done on a jig borer. (Very precise)

For most folks its all good. Some folks can recognize and pursue that last 1/10th MOA. I'm grateful for what I learn from them. I read the same Precision Shooting O-ring article Uncle Nick did. Am I using O-rings? No.

[scatterbrain]

Bart, I removed all my expanders from the sizing dies. I measure every case for length and runout. All seventeen caliber dies that I use produce cases that are within .0005" on both length and runout, if they aren't within the .0005" I resize. I have both a Rockchucker (54 years old) and a coax press. Both will hold the same. I do anneal after every shot. I use a mandrel to size the neck. I have also listened to Unclenick and tried his methods and they work as he said they would, cost a lot of money. But, the results are the same, .0005" is my redo, either way.

[akinswi]

Originally Posted by Bart B.

For what it's worth, best accuracy happens when the expander ball is removed and the full length sizing die neck is honed out to about .002" less than a loaded round's neck diameter. The die is set in the press to set the shoulder back a couple thousandths.

Sierra Bullets pioneered this in the 1960's.

Bart,

What measurement are you basing the .002 From ? lets say I have a 30-06 case and the bullet seated in neck, the diameter measures .312 your saying it needs to be .310 ( these are just hypothetical numbers) what I am asking is how do I know that my die what ever Im using isnt already sizing it down .002 . What number should you start from?

[mehavey]

expander ball is removed and the full length sizing die neck is honed out to about .002" less than a loaded round...

I think that's called a standard Type S – Neck Bushing Die

[Bart B.]

Originally Posted by akinswi

Bart,

What measurement are you basing the .002 From ? What number should you start from?

a loaded round's neck diameter.

Depending on the brass hardness and thickness, the amount may be a thousandth or two different.