Reloading Dies & O-rings
- Thread starter Bart B.
- Start date
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'.
FrankenMauser
New member
Are they needed?
No.
Are they beneficial?
Only if your press (or die) is out of alignment.
No.
Are they beneficial?
Only if your press (or die) is out of alignment.
BillyBoy 57
New member
I am going to follow this thread as I have Questions on the O ring myself ?
LeverGunFan
New member
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.
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
New member
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.
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 .
I have a concentricity gauge and I’ve seen zero positive effect knowing my dies are semi free floating .
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
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
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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.
Sierra Bullets pioneered this in the 1960's.
Sierra, Starline, Hornady and Lake City Arsenal give tours of their facilities.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.
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.
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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.
BillyBoy 57
New member
I will be looking these up , thanks !
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.