Seeking a good source for expanding mandrels

[Mulligan]

Mulligan, the association with interference fit as tension is wrong. Anyone here could test it quick and see it.
Size a neck to any interference fit greater than spring back(>1thou), seat a bullet, measure outside neck diameter. Now pull the bullet and remeasure neck OD. It sprung back ~1thou max. That is your tension, and it applies as a force to the bullet area it's gripping. The greater the area gripped(seated bearing), the greater the tension. With seated bearing established through seating testing (for best), tension is then adjusted by length sized to spring back against that bearing.
When you adjust the sizing length beyond seated bearing (FL sizing of necks), you then put a huge binding force against the small area that is base-bearing junction. This removes all 'adjustment' of tension, and merely sets it to an extreme with variances greatly amplified by any donut variance. I would never do that.

You can adjust the length of neck sizing with a bushing die. Set the bushing size to provide for ~2thou under cal, and then mandrel pre-seat to expand the necks to cal, from which they will always spring back below cal with mandrel exit. Ready for bullet seating.
If you attempt to adjust tension with upsizing, instead of downsizing, what's the difference?
Neck downsizing followed by expansion has been the neck sizing standard longer than we've been alive. The wheel is already on every car.
Not suggesting that we can't improve it, but I am suggesting that would begin with understanding.

Thank you for the explanation
CW

 

[X-Caveman]

Where is a good source for expanding mandrels?
CW

Edit
Explanation, I have a Sinclair expander die and several of the basic expanders for turning necks. I would like to test with different mandrels to "tinker with" neck tension.

CW

I may have something to offer soon. Working with a few manufacturers to get some reasonable pricing. I hope to offer sets from .2405" to .2430" in 1/2 thou increments for the Sinclair tool. They will be hardened & ground toolsteel (62 HRC) with a 5-10 micro inc finish. Asking for working diameters to be held to +/- .0001" - that's the current challenge, finding someone to agree to that tolerance for a reasonable price.

 

[Steve Jennings]

Where is a good source for expanding mandrels?
CW

Edit
Explanation, I have a Sinclair expander die and several of the basic expanders for turning necks. I would like to test with different mandrels to "tinker with" neck tension.

CW

0.0005" increments, each collet does wide range of mandrels, ships in three days, about $100

 

[X-Caveman]

Drop the small end of that range a couple thousandths also.

Tom

10-4

 

[mikecr]

Remember an adage~ 'If you can't make it perfect, float it'.
W/resp to runout this is important.
An expander die doesn't support the case, there is no reason for it to do so, or good in that if it did.
A great thing about the Sinclair Gen II expander die system is that the mandrel is floated within it.

While simple pin/collet changes for expansion seems convenient, that pin would have to be rigidly clamped to keep it from pulling out of the die. The case is still unsupported, it can wiggle about, but not under load(until someone develops a floating caseholder). So I'm not sure about how this situation would contribute to runout.

I capitalized on the Gen II design to add a load cell for pre-seating force measure. The floating mandrels press against the cell. Simple.

 

[JLT]

JLT, what's your feelings about using dry graphite when seating bullets? I recently started using the Imperial (Convenience Pack) on the ends of the cases after pulling some loaded rounds apart and finding maybe 1 out of every 15-20 were stuck. Those were Hornady cases and all prepped at the same time and in the same way. I just pulled 100 Lapua cases to alter the powder charge and noticed a few snug but not stuck like in the term "cold welding". If I hadn't pulled them apart, I would have never know I had a problem except for unexplained fliers or random over pressure signs.

A little graphite will certainly help reduce drag with a mandrel or an expander ball and it will not produce any adverse effects. Heck, smokeless powder is coated with graphite, among other things. I had not considered what practical effect it would have on bullet release but it seems logical that it would help one avoid 'cold weld' or sticking. I have never had a problem with bullets sticking in the neck and I use dry graphite routinely when expanding necks.

 

[Alex Wheeler]

No matter what anyone says sizing a neck to different IDs shows on target. If you size a neck down .005" and use an expander to bring some up to .002" under bullet diam and some up to .003" under bullet diam they will group differently. Why do some guys use .005" neck tension while others use .001"? Because its what shot the best on paper in their rifle.

 

[Mulligan]

No matter what anyone says sizing a neck to different IDs shows on target. If you size a neck down .005" and use an expander to bring some up to .002" under bullet diam and some up to .003" under bullet diam they will group differently. Why do some guys use .005" neck tension while others use .001"? Because its what shot the best on paper in their rifle.

^^^^^^^that is exactly how I see it^^^^^^^^
CW

 

[mikecr]

No matter what anyone says sizing a neck to different IDs shows on target.

Broad statements often fail tests..

 

[dmoran]

Broad statements often fail tests..

Alex's statement sure proves out for me, that I consider "fine tuning the load".

 

[Alex Wheeler]

Broad statements often fail tests..

Mike, agreed. But thats a broad statement I'll stand with. Neck tension changes show on target. This is actually pretty well known.

 

[Steve morgan]

L

Where is a good source for expanding mandrels?
CW

Edit
Explanation, I have a Sinclair expander die and several of the basic expanders for turning necks. I would like to test with different mandrels to "tinker with" neck tension.

CW

Lathe

 

[ashiha]

0.0005" increments, each collet does wide range of mandrels, ships in three days, about $100
View attachment 1010738

Forgive my ignorance, but isn't that basically just a higher-end Lee Collet Neck Sizer Die?

I've heard from a lot of fellows here that they have great results using a polished LCD. Is this not the same concept? If so, does anyone know where one can find precisely sized "mandrels" for the LCD? Mine for 223 is .222" but I'm wondering if I can find other sizes somewhere.

 

[X-Caveman]

No matter what anyone says sizing a neck to different IDs shows on target. If you size a neck down .005" and use an expander to bring some up to .002" under bullet diam and some up to .003" under bullet diam they will group differently. Why do some guys use .005" neck tension while others use .001"? Because its what shot the best on paper in their rifle.

Do you guys think 1/2 thou increments are necessary? I think I could be off to the races pretty quickly with full thou increments. I'm thinking .238"-.243". Those six should cover it, no????

 

[Alex Wheeler]

.001 would be fine for most.

 

[Mulligan]

Do you guys think 1/2 thou increments are necessary? I think I could off to the races pretty quickly with full thou increments. I'm thinking .238"-.243". Those six should cover it, no????

I believe that would work just fine.
CW

 

[Steve Jennings]

Mike, agreed. But thats a broad statement I'll stand with. Neck tension changes show on target. This is actually pretty well known.

Under the heading of too much information we have observed the following:
The ID of fired necks measure a coke bottle and/or an irregular shape: Brass flow or effects of pressure and heat, I don't pretend to know.
The best way to produce the most consistent and straightest shape to hold the bullet is by sizing down about .004" dia below and the expanding up to the desired size, with the correct lube.
Well annealed brass springs back very close to 0.0006"
Bullets can be held in the case with -0.0001" clearance
And yes, we used a CMM to measure the above.

 

[mikecr]

Steve, both you & Alex would have to qualify your arguments(narrow them down), for any credible considerations.
The 'most consistent and straightest' at -4thou fails tests w/resp to my necks having -1thou interference fit for ~.200" length against bullet bearing seated ~.300" deep. It would do nothing for straightness, nor consistency. Truly, -4thou would do no more than overwork necks for my situation. So whatever your stating, it needs to be qualified to the specific situation it applys to.

Alex, you didn't seem to understand that excess interference fit is not tension directly(or possibly at all), and only contributes while sizing greater length than seated bearing. So to suggest differing interference fit changes tune, you should narrow it to the actual situation in which this might occur(not broadly). Like with Steve's implications, yours in no way applies to my partial neck sizing situation(which is not uncommon).

I agree and know for myself that tension affects tune, but everybody does not FL size necks, and seating forces(friction/interference fits) are not tension, or even contributing in some cases. Add annealing, neck thickness, sizing process, and there are too many possible situations to hang one hat on.

 

[Alex Wheeler]

Mike, dont get all guffy on me now. I know neck tension is a slang term for interference fit. Assuming we sized the same amount of neck, the amount of interference fit will change the groups on paper. I understand brass yields after a certain level of interference. I know you believe after a certain point the brass yields and there is no increase in grip. However that does not change the fact that you will see a change in groups up to and past .005" interference fit/neck tension. You have made the statement before and continue to make it that after a point you cant get more grip and that its a waste of time to do so. IF you did more testing and less theorizing it would be obvious to you that you can change your groups with the amount of neck tension/interference/grip/exc. long after the point the brass yields. Why exactly? Who cares. All I know is if your theories stop you at .002 interference you may be leaving some accuracy on the table. Not trying to be rude, but really, this is true. Very common in Benchrest to see a guy run .005" with a ppc.

 

[kvd]

An interesting discussion concerning a subject I must say I've not come to fully appreciate yet.

What is the goal or importance of uniform neck tension or grip? How is it of any concern in light of the several orders of magnitude greater pressure pushing the bullet out of the case and down the barrel? Seems like the 30 ± 10 psi of force required to seat a bullet would be lost in the background noise once the powder combustion gets underway. Is the purpose to resist the force of the primer detonation and keep the bullet seated in the case neck a few microseconds longer? Is the force required to seat a bullet the same as the force required to push it out? It seems from the discussion that the two would not be equal so that it really can't even be measured. People have said neck grip makes a difference and should be controlled. My reasoning can not grasp why this is an important variable. Would appreciate hearing what the group has to say on this subject.

Ken