Question Regarding Expansion Mandrels

[natdscott]

I tell the difference because I use an AMP Press that gives me great detail on my seating pressure, so that I can go up or down in bushing and/or mandrel to hit the target seating pressure that gives me my best SD and most consistent velocity.

You said you tell the difference via all kinds of interesting qualitative factors EXCEPT what actually counts:

The target.

 

[fisherman987]

I own several of these dies and they make excellent reloads and very concentric. The expander mandrel enters the case neck before it is sized on the upstroke. The case neck enters the bushing and is sized, as the neck exits the bushing on the down stroke, the expander mandrel (which is now too small to exit the neck without expanding it due to the neck being resized) expands the neck as it comes out of the bushing leaving a perfectly concentric expanded neck. No deformation of the shoulder occurs.

 

[Ned Ludd]

I asked for a real answer, to a legitimate question, your response provided very little help regarding my question. Sir, you do not know me, nor my shooting abilities, but I assure you that I can tell if there is a difference in my loads.

Thank you.

You might want to relax just a bit. I don't think the response was intended to be derogatory or insulting in any way whatsoever, and it was an answer to the question. I have been using bushing [dies] followed by mandrel treatment to set neck tension/interference fit for several years now with my competition loads and I had exactly the same thought; namely, I'm not sure I could tell the difference. And like you, I am certain that I could tell/shoot the difference if there was a difference worth mentioning.

FWIW - all commonly-used mandrels I am aware of set the neck diameter on the downstroke of the ram. This may be considered semantics, but I would call the component of a bushing die that will set the neck tension on the upstroke an expander ball because it passes through the [wider] un-sized neck opening on the downstroke before the neck has been sized down with the bushing part of the die, then opens the necks up slightly as it is withdrawn/pulled out. One difference between the two is that the outward pulling force on the neck when using an expander ball has a higher propensity to induce runout if everything isn't perfectly aligned. That is not at all to say an expander ball can't work acceptably; they most certainly can. But the chances of inducing runout seem to be higher when pulling an expander ball back through the neck. The obvious downside to using a mandrel after sizing with a bushing die is that it requires an extra step. Regardless of what they choose to call it, the use of an expander ball is not a new concept by SAC, but they do appear to have improved the shape of the expander ball to minimize the pulling force on the neck during withdrawal of the expander ball and the subsequent induction of runout, such as can often be found with more traditional expander ball dies. The cost of owning a number of mandrels of different sizes versus several different sizes of the SAC expander balls/mandrels would also be a consideration.

Some may believe the "simultaneous handoff" between bushing and expander ball to be the best approach. I seriously doubt most people could ever shoot a difference between either method if both were done properly. Frankly, I believe using a mandrel after a bushing die is the "easy button". Although it requires an extra sizing step, little to no consideration about runout is required with the 21st Century Die body/mandrel. They just work.

 

[muleystalker]

If I remember correctly SAC expander Mandrels that are in their sizing dies are not one diameter the full length of the mandrel, the set diameter is at the bottom end of the mandrel and then steps to a smaller diameter a little ways up. This expands the neck then like an expanding button on a Redding die, on the down stroke it drops past the neck as the bushing starts to size the neck in, then on the last step on the up stroke right after the neck exits the bushing then the end of the mandrel with the set diameter is again pulled through the neck giving it its final sizing on the up stroke just like a sizing button in a Redding Die. If you look at SAC instructions for their die it explains this and tells you how to set it up properly.

 

[Ruger15151]

Forester has a similar design where the expander ball enters the bottom of the neck before the top of the neck is completely pulled out of the bushing. This reduces the runout that is usually caused by pulling an expander through the neck vs pushing a mandrel from the top.

When I was using SAC sizing dies with their expander mandrel I was getting an average of .0005 neck runout so the design clearly works and cuts out an extra step.

 

[Timon]

I own several of these dies and they make excellent reloads and very concentric. The expander mandrel enters the case neck before it is sized on the upstroke. The case neck enters the bushing and is sized, as the neck exits the bushing on the down stroke, the expander mandrel (which is now too small to exit the neck without expanding it due to the neck being resized) expands the neck as it comes out of the bushing leaving a perfectly concentric expanded neck. No deformation of the shoulder occurs.

Thank you so much for this explanation of their mandrel. I really appreciate it, no it makes sense to me.

Scott

 

[mikecr]

The bushing these die use are not standard, they have the shoulder and neck bulit into the bushing.

If that means FL sizing of necks, I would avoid that like a plague.

 

[Timon]

You might want to relax just a bit. I don't think the response was intended to be derogatory or insulting in any way whatsoever, and it was an answer to the question. I have been using bushing [dies] followed by mandrel treatment to set neck tension/interference fit for several years now with my competition loads and I had exactly the same thought; namely, I'm not sure I could tell the difference. And like you, I am certain that I could tell/shoot the difference if there was a difference worth mentioning.

FWIW - all commonly-used mandrels I am aware of set the neck diameter on the downstroke of the ram. This may be considered semantics, but I would call the component of a bushing die that will set the neck tension on the upstroke an expander ball because it passes through the [wider] un-sized neck opening on the downstroke before the neck has been sized down with the bushing part of the die, then opens the necks up slightly as it is withdrawn/pulled out. One difference between the two is that the outward pulling force on the neck when using an expander ball has a higher propensity to induce runout if everything isn't perfectly aligned. That is not at all to say an expander ball can't work acceptably; they most certainly can. But the chances of inducing runout seem to be higher when pulling an expander ball back through the neck. The obvious downside to using a mandrel after sizing with a bushing die is that it requires an extra step. Regardless of what they choose to call it, the use of an expander ball is not a new concept by SAC, but they do appear to have improved the shape of the expander ball to minimize the pulling force on the neck during withdrawal of the expander ball and the subsequent induction of runout, such as can often be found with more traditional expander ball dies. The cost of owning a number of mandrels of different sizes versus several different sizes of the SAC expander balls/mandrels would also be a consideration.

Some may believe the "simultaneous handoff" between bushing and expander ball to be the best approach. I seriously doubt most people could ever shoot a difference between either method if both were done properly. Frankly, I believe using a mandrel after a bushing die is the "easy button". Although it requires an extra sizing step, little to no consideration about runout is required with the 21st Century Die body/mandrel. They just work.

Thank you for your response. If you look at my original post, I was not stating that I could tell the difference between the two methods, I was nearly asking for peoples thoughts about the two. The poster that brought up this idea, that I could not tell the difference, was the one that created that idea. That was never my intention.

I agree with you that the 21st Century mandrels just work, which is why I have been using them for years. However, as I own the SAC sizing die, I felt that it was worth getting some thoughts, from others on the forum, that may be using the SAC mandrels for the die. The SAC mandrels are $50 each and require the one time purchase of a collet for another $25. If others users told me it was not working as intended, I would not spend the money. I decided to go ahead and order the SAC mandrels and do some testing with them to see how they work.

I do thank you very much, for all the very useful information that you provided.

Scott

 

[Ned Ludd]

Thank you for your response. If you look at my original post, I was not stating that I could tell the difference between the two methods, I was nearly asking for peoples thoughts about the two. The poster that brought up this idea, that I could not tell the difference, was the one that created that idea. That was never my intention.

I agree with you that the 21st Century mandrels just work, which is why I have been using them for years. However, as I own the SAC sizing die, I felt that it was worth getting some thoughts, from others on the forum, that may be using the SAC mandrels for the die. The SAC mandrels are $50 each and require the one time purchase of a collet for another $25. If others users told me it was not working as intended, I would not spend the money. I decided to go ahead and order the SAC mandrels and do some testing with them to see how they work.

I do thank you very much, for all the very useful information that you provided.

Scott

I get it, spending hard-earned $$$ is never easy, and one would like some evidence of value or benefit before doing so. If you are willing, please share your thoughts on the performance of the SAC mandrel/expander ball setup as compared to the 21st Century mandrels once you have developed an impression of how they are working in your hands. Thanks!

 

[swd]

The Porter Precision expander mandrel uses readily available gage pins you can get from Amazon for $2.00-4.00 each. The body and collet assembly aren’t cheap but you don’t have buy any proprietary parts after that. You do need to taper the gage pin on a sander in a hand drill which takes about 30 seconds and give it light polish. But it’s easy to do.

 

[Dave M.]

I am currently using 21st Century Expansion Mandrels and have been for quite a while now. I switched to a Short Action Customs modular bushing sizing die recently. On this die, SAC uses a mandrel that replaces the decapping rod and pin.

I was going to switch to SAC mandrels for this die, but got to thinking that they would set the ID on the downstroke of the press ram. I have always read that it is better to use a mandrel that sets the ID on the upstroke of the ram. SAC makes fantastic tools and their sizing die is fantastic, just not sure about this mandrel thing.

I contacted SAC about this and they told me the best possible use of a mandrel, is an instantaneous handoff of the neck from the bushing that sets the OD, to the mandrel that sets the ID. Just not sure what to think of this. I suppose it sounds reasonable, but I have always read and subscribed to the theory, that the case is stronger with the mandrel being pushed into it, rather that being pulled out of it.

Just looking for some others thoughts on this.

Thanks

Scott

The SAC guys know their shit and I’d listen to their advice until your testing proves them wrong

 

[Ruger15151]

The Porter Precision expander mandrel uses readily available gage pins you can get from Amazon for $2.00-4.00 each. The body and collet assembly aren’t cheap but you don’t have buy any proprietary parts after that. You do need to taper the gage pin on a sander in a hand drill which takes about 30 seconds and give it light polish. But it’s easy to do.

I have that die and its great. much cheaper to buy pins at $4 for testing.

Mandrel Dies – Porter's Precision Products

www.portersprecisionproducts.com

 

[mikecr]

Whatever you use, the mandrel needs to float, so you don't push or pull necks off center.