MANDREL DECISIONS

[Phil Rizzo]

To have an accurate recorded measurement using a certain combination?
Gauged arbor presses can show the difference easily.

 

[ntsqd]

For folks who do neck expansion, you can take tuning to a much smaller increment using gauge pins, this is another option.

Mandrel Dies – Porter's Precision Products

portersprecisionproducts.com

Quoted because I've been suggesting this tool since I found or was directed to them at least 2 years ago. I like that I can buy high quality, tight OD tolerance "mandrels" from non reloading vendors like MSC-Direct fairly inexpensively, grind a lead-in taper on them, and put them to use.

I must admit that I am troubled by what I'll call the "Beer Can Syndrome" when it comes to sizing the neck ID by pushing in rather than pulling out. We all know what happens to a beer can when you stand on it. If you're absolutely perfectly level when standing on it the can will support you. Tilt your foot just slightly and the can will crumple and they NEVER crumple perfectly coaxially. Relative to the bottom, the top is always offset in the direction of the tilt. I'm pretty much dead sure that no reloading press made is that perfect, not while under a load anyway. Yet it seems to work well enough, so maybe I'm seeing the boogie man where there isn't one.

 

[cajun]

I'm kinda in the same boat. Been debating if it's worth it to go down that rabbit hole. I will most likely take a rifle I have a known accuracy load for and see if a bushing and mandrel can make a difference. It's just so freaking hot right now.

 

[MarkInPA]

Quoted because I've been suggesting this tool since I found or was directed to them at least 2 years ago. I like that I can buy high quality, tight OD tolerance "mandrels" from non reloading vendors like MSC-Direct fairly inexpensively, grind a lead-in taper on them, and put them to use.

I must admit that I am troubled by what I'll call the "Beer Can Syndrome" when it comes to sizing the neck ID by pushing in rather than pulling out. We all know what happens to a beer can when you stand on it. If you're absolutely perfectly level when standing on it the can will support you. Tilt your foot just slightly and the can will crumple and they NEVER crumple perfectly coaxially. Relative to the bottom, the top is always offset in the direction of the tilt. I'm pretty much dead sure that no reloading press made is that perfect, not while under a load anyway. Yet it seems to work well enough, so maybe I'm seeing the boogie man where there isn't one.

So you are suggesting that pulling a expander ball through the neck to set final I.D. might be the better option anyway? Probably the Forster sizing die with the expander held up high in the sizing die would be the best option if using the expander ball.

 

[Turpentine21]

Good point.
I assume some people prefer higher clearance simply trying to avoid the bullet being either pushed down in the case neck (e.g. by tight fitting ammo cases), or hung in the barrel throat when unloading a cartridge if loaded long, touching the grooves (it happened to me )...
I use mandrels to with 2 thousands less than the bullet for all cartridges, mostly for consistency/simplification.
I think that is the only role played by increased static friction. When the gun goes boom, the force pushing the bullet out is immensely higher than the friction opposing the movement, not to mention the neck expansion in microseconds, as you said. Even in a case with only the primer and the bullet seated (no propellant), the primer detonation is enough to push the bullet out of the case (and stuck in the grooves).

I like .0025-.003 in ARs. A bullet moving in the case under recoil or feeding is not good. Ask me how I know! Just don't ask right after I just tried to eject a case manually, left the projectile in the barrel, and dumped powder throughout the receiver. . I am on your side

 

[ntsqd]

So you are suggesting that pulling a expander ball through the neck to set final I.D. might be the better option anyway? Probably the Forster sizing die with the expander held up high in the sizing die would be the best option if using the expander ball.

Based on reports from people far more experienced than I am, no. I'm just having trouble with why that should be when intuition and experience with things not reloading tell me that it should be the less desirable method.

 

[Bitteroot]

@ARlife4me
Perhaps you're over thinking this topic as many do.
In my experience very few combinations like super light hold as mine does not' but those that do then a mandrel makes sense and maybe I just look at things a little differently and since we live in America thats ok ( at least for now) but to illustrate I'll post a test from a few years ago.
In the first attachment groups one and two are the same bushing size, groups three four and five have progressively smaller bushings.
Even with a tickle of R-L at the target distance we can accept that group four shot smaller than the others and confirmed in the next attachment, it's also pretty easy to accept that not one size fits all applications and more hold can be better for those combinations that prefer the extra start pressure.
There were no mandrels involved just a bushing to size the brass and a target to interpret.
I realize there are those much smarter than myself but at what point did spring back enter the equation for consideration ?
My point is that if a guy wants to know something, going out to the range and testing is the best way I've found.

 

[ARlife4me]

@ARlife4me
Perhaps you're over thinking this topic as many do.
In my experience very few combinations like super light hold as mine does not' but those that do then a mandrel makes sense and maybe I just look at things a little differently and since we live in America thats ok ( at least for now) but to illustrate I'll post a test from a few years ago.
In the first attachment groups one and two are the same bushing size, groups three four and five have progressively smaller bushings.
Even with a tickle of R-L at the target distance we can accept that group four shot smaller than the others and confirmed in the next attachment, it's also pretty easy to accept that not one size fits all applications and more hold can be better for those combinations that prefer the extra start pressure.
There were no mandrels involved just a bushing to size the brass and a target to interpret.
I realize there are those much smarter than myself but at what point did spring back enter the equation for consideration ?

I'm posting mostly out of curiosity. All I've done for 42 years is fl size w/button on every reload.

 

[dstancu]

Based on reports from people far more experienced than I am, no. I'm just having trouble with why that should be when intuition and experience with things not reloading tell me that it should be the less desirable method.

I think your question is valid.
Here is what I think, also based on other (smarter) people contributions.

When the mandrel is pushed down the case throat, the case area under direct pressure has a support structure (neck supported by the shoulder and shoulder by the case body). Plus, mandrel has an ogive top to get in the neck smoothly, and we can use graphite as lubricant. Once in the neck, the mandrel keeps the case coaxial, having some well machined cylinder length. The result is almost no longitudinal change for the case, but only neck diameter change.

In the case of an expander ball mounted on the center stem (like in the Forster sizing dies), the only time the expander ball touches the neck is on its way out, after the case has already been resized and the neck tightened. There is potential for inconsistency. Pulling the ball out can very slightly elongate the neck-shoulder area, as there is not much in the geometry to prevent that. In addition, a ball has way less contact area with the inside of the neck compared to the cylinder of a mandrel or gauge pin, increasing variability of the outcome.

I removed the center stem on all my sizing dies (for depriming I use a Frankford Arsenal Platinum hand tool anyway, so I can watch TV while doing that step :)).

 

[Phil Rizzo]

Simply put, if you desire consistency then annealing, bushing dies and mandrels is the best way I know of.

Unless you want custom dies, polished button or ball expanders or whatever they are called. It's much easier to me swapping .0005 to .001 at a time to reach your sweet spot. I don't have runout issues with bushing dies, though some have seen this personally.
@MagnumManiac has information on this topic.
I guess shell holders, presses, rams etc can cause this as well as dies, possibly?

 

[MarkInPA]

Simply put, if you desire consistency then annealing, bushing dies and mandrels is the best way I know of.

Unless you want custom dies, polished button or ball expanders or whatever they are called. It's much easier to me swapping .0005 to .001 at a time to reach your sweet spot. I don't have runout issues with bushing dies, though some have seen this personally.
@MagnumManiac has information on this topic.
I guess shell holders, presses, rams etc can cause this as well as dies, possibly?

I have kind of been waiting to see what he has to say.

 

[Phil Rizzo]

Not being a comp shooter, I call .001 or less "good".

I really don't even check any more, unless I get issues that seem weird, say maybe with a proven load. Not often, at all.

*LE Wilson seaters are fine units for reducing/eliminating runout, also.

 

[Mike Matteson]

21st Century Innovation has .375 caliber mandrels. I recently asked them.

21st Century seem to have the biggest supply of mandrels in sizes by the .001 steps. Set up a excel program to determine what you want for neck tension. I don't know it the math part will go through.

 

[MarkInPA]

21st Century seem to have the biggest supply of mandrels in sizes by the .001 steps. Set up a excel program to determine what you want for neck tension. I don't know it the math part will go through.

Thanks Mike